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:
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>
The following example illustrates the use of a simple CASE expression:
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>
Use CASE statement to deal with NULL
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>
Use Case to output null value
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>
Use case when and grouping function together
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>
Use case when clause to decode value
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.
Use case when statement with between ... and
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>
Use case when statement with exists and subquery
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>
Use case when statement with in()
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>
Use case when statement with to_char() like
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>
Use case when with comparasion operator
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>
Use logical operators in a searched CASE expression
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>
Using Searched CASE Expressions
Searched CASE expressions use conditions to determine the returned value and have the following syntax:
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
...
WHEN conditionN THEN resultN
ELSE default_result
END
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:
CASE search_expression
WHEN expression1 THEN result1
WHEN expression2 THEN result2
...
WHEN expressionN THEN resultN
ELSE default_result
END
Wrap case when into sum() function
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.