Oracle PL/SQL Tutorial/Query Select/CASE
Содержание
- 1 The following example illustrates the use of a searched CASE expression:
- 2 The following example illustrates the use of a simple CASE expression:
- 3 Use CASE statement to deal with NULL
- 4 Use Case to output null value
- 5 Use case when and grouping function together
- 6 Use case when clause to decode value
- 7 Use case when statement with between ... and
- 8 Use case when statement with exists and subquery
- 9 Use case when statement with in()
- 10 Use case when statement with to_char() like
- 11 Use case when with comparasion operator
- 12 Use logical operators in a searched CASE expression
- 13 Using Searched CASE Expressions
- 14 Using the CASE Expression
- 15 Wrap case when into sum() function
The following example illustrates the use of a searched CASE expression:
<source lang="sql">
SQL> SQL> SQL> -- create demo table SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) NOT NULL, 3 First_Name VARCHAR2(10 BYTE), 4 Last_Name VARCHAR2(10 BYTE), 5 Start_Date DATE, 6 End_Date DATE, 7 Salary Number(8,2), 8 City VARCHAR2(10 BYTE), 9 Description VARCHAR2(15 BYTE) 10 ) 11 /
Table created. SQL> SQL> -- prepare data SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto", "Programmer") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York", "Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York", "Manager") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester") 3 /
1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee
2 /
ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION
---------- ---------- --------- --------- ---------- ---------- ---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected. SQL> SQL> SQL> SQL> SELECT id,
2 CASE 3 WHEN id = 1 THEN "E" 4 WHEN id = 2 THEN "D" 5 WHEN id = 3 THEN "C" 6 WHEN id = 4 THEN "D" 7 ELSE "Default" 8 END 9 FROM employee;
ID CASEWHE
-------
01 E 02 D 03 C 04 D 05 Default 06 Default 07 Default 08 Default 8 rows selected. SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL></source>
The following example illustrates the use of a simple CASE expression:
<source lang="sql">
SQL> SQL> SQL> -- create demo table SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) NOT NULL primary key, 3 First_Name VARCHAR2(10 BYTE), 4 Last_Name VARCHAR2(10 BYTE), 5 Start_Date DATE, 6 End_Date DATE, 7 Salary Number(8,2), 8 City VARCHAR2(10 BYTE), 9 Description VARCHAR2(15 BYTE) 10 ) 11 /
Table created. SQL> SQL> -- prepare data SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto", "Programmer") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York", "Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York", "Manager") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester") 3 /
1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee
2 /
ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION
-------------------- -------------------- --------- --------- ---------- ---------- ---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected. SQL> SQL> SQL> SELECT id,
2 CASE id 3 WHEN "01" THEN "A" 4 WHEN "02" THEN "B" 5 WHEN "03" THEN "C" 6 WHEN "04" THEN "D" 7 ELSE "Default" 8 END 9 FROM employee;
ID CASEIDW
-------
01 A 02 B 03 C 04 D 05 Default 06 Default 07 Default 08 Default 8 rows selected. SQL> SQL> SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL></source>
Use CASE statement to deal with NULL
<source lang="sql">
SQL> SQL> -- create demo table SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) NOT NULL, 3 First_Name VARCHAR2(10 BYTE), 4 Last_Name VARCHAR2(10 BYTE), 5 Start_Date DATE, 6 End_Date DATE, 7 Salary Number(8,2), 8 City VARCHAR2(10 BYTE), 9 Description VARCHAR2(15 BYTE) 10 ) 11 /
Table created. SQL> SQL> -- prepare data SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060
725","YYYYMMDD"), 1234.56, "Toronto", "Programmer")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860
221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900
315","YYYYMMDD"), 6544.78, NULL,"Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990
421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980
808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960
104","YYYYMMDD"), 4322.78,"New York", "Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980
212","YYYYMMDD"), 7897.78,"New York", "Manager")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020
415","YYYYMMDD"), 1232.78,NULL, "Tester")
3 /
1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee
2 /
ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION
---------- ---------- --------- --------- ---------- ---------- ---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Tester 8 rows selected. SQL> SQL> SQL> SELECT count(*),
2 CASE NVL(city,"x") 3 WHEN "x" then "Null" 4 ELSE city 5 END CITY -- CASE 6 FROM employee 7 GROUP BY city; COUNT(*) CITY
----------
2 Null 2 New York 1 Toronto 3 Vancouver
SQL> SQL> SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL></source>
Use Case to output null value
<source lang="sql">
SQL> SQL> SQL> -- create demo table SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) NOT NULL, 3 First_Name VARCHAR2(10 BYTE), 4 Last_Name VARCHAR2(10 BYTE), 5 Start_Date DATE, 6 End_Date DATE, 7 Salary Number(8,2), 8 City VARCHAR2(10 BYTE), 9 Description VARCHAR2(15 BYTE) 10 ) 11 /
Table created. SQL> SQL> -- prepare data SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060
725","YYYYMMDD"), 1234.56, "Toronto", "Programmer")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860
221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900
315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990
421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980
808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960
104","YYYYMMDD"), 4322.78,"New York", "Tester")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980
212","YYYYMMDD"), 7897.78,"New York", "Manager")
3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date,
Salary, City, Description) 2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020
415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
3 /
1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee
2 /
ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION
---------- ---------- --------- --------- ---------- ---------- ---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected. SQL> SQL> SQL> SQL> SQL> SELECT count(*),
2 CASE City 3 WHEN "Vancouver" then "No" 4 WHEN "New York" then "Yes" 5 WHEN null then "Null" 6 END CITY -- CASE 7 FROM employee 8 GROUP BY city; COUNT(*) CITY
----
2 Yes 1 5 No
SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL> SQL></source>
Use case when and grouping function together
<source lang="sql">
SQL> SQL> create table emp
2 ( empno NUMBER(4) constraint E_PK primary key 3 , ename VARCHAR2(8) 4 , init VARCHAR2(5) 5 , job VARCHAR2(8) 6 , mgr NUMBER(4) 7 , bdate DATE 8 , sal NUMBER(6,2) 9 , comm NUMBER(6,2) 10 , deptno NUMBER(2) default 10 11 ) ;
Table created. SQL> insert into emp values(1,"Tom","N", "TRAINER", 13,date "1965-12-17", 800 , NULL, 20); 1 row created. SQL> insert into emp values(2,"Jack","JAM", "Tester",6,date "1961-02-20", 1600, 300, 30); 1 row created. SQL> insert into emp values(3,"Wil","TF" , "Tester",6,date "1962-02-22", 1250, 500, 30); 1 row created. SQL> insert into emp values(4,"Jane","JM", "Designer", 9,date "1967-04-02", 2975, NULL, 20); 1 row created. SQL> insert into emp values(5,"Mary","P", "Tester",6,date "1956-09-28", 1250, 1400, 30); 1 row created. SQL> insert into emp values(6,"Black","R", "Designer", 9,date "1963-11-01", 2850, NULL, 30); 1 row created. SQL> insert into emp values(7,"Chris","AB", "Designer", 9,date "1965-06-09", 2450, NULL, 10); 1 row created. SQL> insert into emp values(8,"Smart","SCJ", "TRAINER", 4,date "1959-11-26", 3000, NULL, 20); 1 row created. SQL> insert into emp values(9,"Peter","CC", "Designer",NULL,date "1952-11-17", 5000, NULL, 10); 1 row created. SQL> insert into emp values(10,"Take","JJ", "Tester",6,date "1968-09-28", 1500, 0, 30); 1 row created. SQL> insert into emp values(11,"Ana","AA", "TRAINER", 8,date "1966-12-30", 1100, NULL, 20); 1 row created. SQL> insert into emp values(12,"Jane","R", "Manager", 6,date "1969-12-03", 800 , NULL, 30); 1 row created. SQL> insert into emp values(13,"Fake","MG", "TRAINER", 4,date "1959-02-13", 3000, NULL, 20); 1 row created. SQL> insert into emp values(14,"Mike","TJA","Manager", 7,date "1962-01-23", 1300, NULL, 10); 1 row created. SQL> SQL> select deptno
2 , case grouping(job) 3 when 0 then job 4 when 1 then "total" 5 end job 6 , count(empno) headcount 7 from emp 8 group by ROLLUP(deptno, job); DEPTNO JOB HEADCOUNT
-------- ----------
10 Manager 1 10 Designer 2 10 total 3 20 TRAINER 4 20 Designer 1 20 total 5 30 Tester 4 30 Manager 1 30 Designer 1 30 total 6 total 14
11 rows selected. SQL> SQL> SQL> drop table emp; Table dropped. SQL></source>
Use case when clause to decode value
<source lang="sql">
SQL> create table registrations
2 ( attendee NUMBER(4) 3 , course VARCHAR2(6) 4 , begindate DATE 5 , evaluation NUMBER(1) 6 , constraint R_PK primary key (attendee,course,begindate) 7 ) ;
Table created. SQL> SQL> insert into registrations values (2,"SQL",date "2009-04-12",4 ); 1 row created. SQL> insert into registrations values (14,"SQL",date "2009-04-12",5 ); 1 row created. SQL> insert into registrations values (6,"SQL",date "2009-04-12",4 ); 1 row created. SQL> insert into registrations values (11,"SQL",date "2009-04-12",2 ); 1 row created. SQL> insert into registrations values (8,"SQL",date "2009-10-04",NULL); 1 row created. SQL> insert into registrations values (9,"SQL",date "2009-10-04",3 ); 1 row created. SQL> insert into registrations values (13,"SQL",date "2009-10-04",4 ); 1 row created. SQL> insert into registrations values (13,"SQL",date "2009-12-13",NULL); 1 row created. SQL> insert into registrations values (6,"SQL",date "2009-12-13",NULL); 1 row created. SQL> insert into registrations values (3,"OAU",date "2009-08-10",4 ); 1 row created. SQL> insert into registrations values (12,"OAU",date "2009-08-10",4 ); 1 row created. SQL> insert into registrations values (13,"OAU",date "2009-08-10",5 ); 1 row created. SQL> SQL> select attendee, begindate
2 , case evaluation 3 when 1 then "bad" 4 when 2 then "mediocre" 5 when 3 then "ok" 6 when 4 then "good" 7 when 5 then "excellent" 8 else "not filled in" 9 end 10 from registrations 11 where course = "SQL"; ATTENDEE BEGINDATE CASEEVALUATIO
---------- -------------
2 12-04-2009 good 14 12-04-2009 excellent 6 12-04-2009 good 11 12-04-2009 mediocre 8 04-10-2009 not filled in 9 04-10-2009 ok 13 04-10-2009 good 13 13-12-2009 not filled in 6 13-12-2009 not filled in
9 rows selected. SQL> SQL> SQL> drop table registrations; Table dropped.</source>
Use case when statement with between ... and
<source lang="sql">
SQL> SQL> create table emp(
2 emp_no integer primary key 3 ,lastname varchar2(20) not null 4 ,firstname varchar2(15) not null 5 ,midinit varchar2(1) 6 ,street varchar2(30) 7 ,city varchar2(20) 8 ,state varchar2(2) 9 ,zip varchar2(5) 10 ,shortZipCode varchar2(4) 11 ,area_code varchar2(3) 12 ,phone varchar2(8) 13 ,salary number(5,2) 14 ,birthdate date 15 ,startDate date 16 ,title varchar2(20) 17 ,dept_no integer 18 ,mgr integer 19 ,region number 20 ,division number 21 ,total_sales number 22 );
Table created. SQL> SQL> SQL> SQL> SQL> -- emp Table Inserts: SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values
2 (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");
1 row created. SQL> SQL> SQL> SQL> SQL> create table avg_sal
2 as select avg(salary) AS avg_Sal from emp;
Table created. SQL> SQL> SQL> select
2 case when salary between 6 and 8 then "6-8" 3 when salary in (9,10) then "9-10" 4 when exists (select null from avg_sal where avg_sal = salary) 5 then "EXISTS" 6 when to_char(salary) like "2%" then "Like2" 7 when salary is null then "Null" 8 else "ELSE Empno: "|| emp_no 9 end 10 AS case_test 11 from emp 12 /
CASE_TEST
Null SQL> SQL> SQL> drop table avg_sal; Table dropped. SQL> SQL> drop table emp; Table dropped. SQL> SQL> SQL></source>
Use case when statement with exists and subquery
<source lang="sql">
SQL> SQL> create table emp(
2 emp_no integer primary key 3 ,lastname varchar2(20) not null 4 ,firstname varchar2(15) not null 5 ,midinit varchar2(1) 6 ,street varchar2(30) 7 ,city varchar2(20) 8 ,state varchar2(2) 9 ,zip varchar2(5) 10 ,shortZipCode varchar2(4) 11 ,area_code varchar2(3) 12 ,phone varchar2(8) 13 ,salary number(5,2) 14 ,birthdate date 15 ,startDate date 16 ,title varchar2(20) 17 ,dept_no integer 18 ,mgr integer 19 ,region number 20 ,division number 21 ,total_sales number 22 );
Table created. SQL> SQL> SQL> SQL> SQL> -- emp Table Inserts: SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values
2 (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");
1 row created. SQL> SQL> SQL> SQL> SQL> create table avg_sal
2 as select avg(salary) AS avg_Sal from emp;
Table created. SQL> SQL> SQL> select
2 case when salary between 6 and 8 then "6-8" 3 when salary in (9,10) then "9-10" 4 when exists (select null from avg_sal where avg_sal = salary) 5 then "EXISTS" 6 when to_char(salary) like "2%" then "Like2" 7 when salary is null then "Null" 8 else "ELSE Empno: "|| emp_no 9 end 10 AS case_test 11 from emp 12 /
CASE_TEST
Null SQL> SQL> SQL> drop table avg_sal; Table dropped. SQL> SQL> drop table emp; Table dropped. SQL> SQL> SQL></source>
Use case when statement with in()
<source lang="sql">
SQL> SQL> create table emp(
2 emp_no integer primary key 3 ,lastname varchar2(20) not null 4 ,firstname varchar2(15) not null 5 ,midinit varchar2(1) 6 ,street varchar2(30) 7 ,city varchar2(20) 8 ,state varchar2(2) 9 ,zip varchar2(5) 10 ,shortZipCode varchar2(4) 11 ,area_code varchar2(3) 12 ,phone varchar2(8) 13 ,salary number(5,2) 14 ,birthdate date 15 ,startDate date 16 ,title varchar2(20) 17 ,dept_no integer 18 ,mgr integer 19 ,region number 20 ,division number 21 ,total_sales number 22 );
Table created. SQL> SQL> SQL> SQL> SQL> -- emp Table Inserts: SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values
2 (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");
1 row created. SQL> SQL> SQL> SQL> SQL> create table avg_sal
2 as select avg(salary) AS avg_Sal from emp;
Table created. SQL> SQL> SQL> select
2 case when salary between 6 and 8 then "6-8" 3 when salary in (9,10) then "9-10" 4 when exists (select null from avg_sal where avg_sal = salary) 5 then "EXISTS" 6 when to_char(salary) like "2%" then "Like2" 7 when salary is null then "Null" 8 else "ELSE Empno: "|| emp_no 9 end 10 AS case_test 11 from emp 12 /
CASE_TEST
Null SQL> SQL> SQL> drop table avg_sal; Table dropped. SQL> SQL> drop table emp; Table dropped. SQL> SQL> SQL></source>
Use case when statement with to_char() like
<source lang="sql">
SQL> SQL> create table emp(
2 emp_no integer primary key 3 ,lastname varchar2(20) not null 4 ,firstname varchar2(15) not null 5 ,midinit varchar2(1) 6 ,street varchar2(30) 7 ,city varchar2(20) 8 ,state varchar2(2) 9 ,zip varchar2(5) 10 ,shortZipCode varchar2(4) 11 ,area_code varchar2(3) 12 ,phone varchar2(8) 13 ,salary number(5,2) 14 ,birthdate date 15 ,startDate date 16 ,title varchar2(20) 17 ,dept_no integer 18 ,mgr integer 19 ,region number 20 ,division number 21 ,total_sales number 22 );
Table created. SQL> SQL> SQL> SQL> SQL> -- emp Table Inserts: SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values
2 (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");
1 row created. SQL> SQL> SQL> SQL> SQL> create table avg_sal
2 as select avg(salary) AS avg_Sal from emp;
Table created. SQL> SQL> SQL> select
2 case when salary between 6 and 8 then "6-8" 3 when salary in (9,10) then "9-10" 4 when exists (select null from avg_sal where avg_sal = salary) 5 then "EXISTS" 6 when to_char(salary) like "2%" then "Like2" 7 when salary is null then "Null" 8 else "ELSE Empno: "|| emp_no 9 end 10 AS case_test 11 from emp 12 /
CASE_TEST
Null SQL> SQL> SQL> drop table avg_sal; Table dropped. SQL> SQL> drop table emp; Table dropped. SQL> SQL> SQL></source>
Use case when with comparasion operator
<source lang="sql">
SQL> SQL> create table emp(
2 emp_no integer primary key 3 ,lastname varchar2(20) not null 4 ,firstname varchar2(15) not null 5 ,midinit varchar2(1) 6 ,street varchar2(30) 7 ,city varchar2(20) 8 ,state varchar2(2) 9 ,zip varchar2(5) 10 ,shortZipCode varchar2(4) 11 ,area_code varchar2(3) 12 ,phone varchar2(8) 13 ,salary number(5,2) 14 ,birthdate date 15 ,startDate date 16 ,title varchar2(20) 17 ,dept_no integer 18 ,mgr integer 19 ,region number 20 ,division number 21 ,total_sales number 22 );
Table created. SQL> SQL> SQL> SQL> SQL> SQL> create table avg_sal
2 as select avg(salary) AS avg_Sal from emp;
Table created. SQL> SQL> select lastname, salary,
2 CASE WHEN salary > avg_sal THEN "> Average of " || to_char(avg_sal, "99.99") 3 WHEN salary < avg_sal THEN "< Average of " || to_char(avg_sal, "99.99") 4 ELSE "= Average of " || to_char(avg_sal, "99.99") 5 END 6 from emp, avg_sal 7 /
no rows selected SQL> SQL> drop table emp; Table dropped. SQL> SQL> SQL> SQL> SQL> drop table avg_Sal; Table dropped. SQL></source>
Use logical operators in a searched CASE expression
<source lang="sql">
SQL> SQL> SQL> -- create demo table SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) NOT NULL, 3 First_Name VARCHAR2(10 BYTE), 4 Last_Name VARCHAR2(10 BYTE), 5 Start_Date DATE, 6 End_Date DATE, 7 Salary Number(8,2), 8 City VARCHAR2(10 BYTE), 9 Description VARCHAR2(15 BYTE) 10 ) 11 /
Table created. SQL> SQL> -- prepare data SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values ("01","Jason", "Martin", to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto", "Programmer") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("02","Alison", "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("03","James", "Smith", to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("04","Celia", "Rice", to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("05","Robert", "Black", to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("06","Linda", "Green", to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York", "Tester") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("07","David", "Larry", to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York", "Manager") 3 /
1 row created. SQL> insert into Employee(ID, First_Name, Last_Name, Start_Date, End_Date, Salary, City, Description)
2 values("08","James", "Cat", to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester") 3 /
1 row created. SQL> SQL> SQL> SQL> -- display data in the table SQL> select * from Employee
2 /
ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION
---------- ---------- --------- --------- ---------- ---------- ---------------
01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected. SQL> SQL> SQL> SQL> SELECT id, salary,
2 CASE 3 WHEN salary > 45000 THEN "HIGH" 4 ELSE "LOW" 5 END 6 FROM employee;
ID SALARY CASE
---------- ----
01 1234.56 LOW 02 6661.78 LOW 03 6544.78 LOW 04 2344.78 LOW 05 2334.78 LOW 06 4322.78 LOW 07 7897.78 LOW 08 1232.78 LOW 8 rows selected. SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL></source>
Using Searched CASE Expressions
Searched CASE expressions use conditions to determine the returned value and have the following syntax:
<source lang="sql">
CASE
WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... WHEN conditionN THEN resultN ELSE default_result
END</source>
where
- condition1, condition2, ..., conditionN are the expressions to be evaluated.
- result1, result2, ..., resultN are the returned results (one for each possible condition).
- If condition1 is true, result1 is returned, and so on.
- default_result is the default result returned when no true condition is found.
Using the CASE Expression
CASE expression perform if-then-else logic in SQL without having to use PL/SQL.
CASE works in a similar manner to DECODE().
CASE is ANSI-compliant.
There are two types of CASE expressions:
- Simple case expressions use expressions to determine the returned value.
- Searched case expressions use conditions to determine the returned value.
Simple CASE expressions use expressions to determine the returned value and have the following syntax:
<source lang="sql">
CASE search_expression
WHEN expression1 THEN result1 WHEN expression2 THEN result2 ... WHEN expressionN THEN resultN ELSE default_result
END</source>
Wrap case when into sum() function
<source lang="sql">
SQL> SQL> create table emp(
2 emp_no integer primary key 3 ,lastname varchar2(20) not null 4 ,firstname varchar2(15) not null 5 ,midinit varchar2(1) 6 ,street varchar2(30) 7 ,city varchar2(20) 8 ,state varchar2(2) 9 ,zip varchar2(5) 10 ,shortZipCode varchar2(4) 11 ,area_code varchar2(3) 12 ,phone varchar2(8) 13 ,salary number(5,2) 14 ,birthdate date 15 ,startDate date 16 ,title varchar2(20) 17 ,dept_no integer 18 ,mgr integer 19 ,region number 20 ,division number 21 ,total_sales number 22 );
Table created. SQL> SQL> -- emp Table Inserts: SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values
2 (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");
1 row created. SQL> SQL> SQL> select
2 sum ( case when salary between 6 and 10 then 1 else 0 end ) 3 as sal_6_10, 4 sum ( case when salary between 11 and 15 then 1 else 0 end ) 5 as sal_11_15, 6 sum ( case when salary between 16 and 20 then 1 else 0 end ) 7 as sal_16_20, 8 sum ( case when salary between 21 and 25 then 1 else 0 end ) 9 as sal_21_25 10 from emp; SAL_6_10 SAL_11_15 SAL_16_20 SAL_21_25
---------- ---------- ----------
0 0 0 0
1 row selected. SQL> drop table emp; Table dropped.</source>