Oracle PL/SQL/Insert Delete Update/Delete Subquery

Writing a DELETE Statement Containing a Subquery

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_DATE  END_DATE        SALARY CITY       DESCRIPTION
---- ---------- ---------- ----------- ----------- ---------- ---------- ---------------
01   Jason      Martin     1996-JUL-25 2006-JUL-25    1234.56 Toronto    Programmer
02   Alison     Mathews    1976-MAR-21 1986-FEB-21    6661.78 Vancouver  Tester
03   James      Smith      1978-DEC-12 1990-MAR-15    6544.78 Vancouver  Tester
04   Celia      Rice       1982-OCT-24 1999-APR-21    2344.78 Vancouver  Manager
05   Robert     Black      1984-JAN-15 1998-AUG-08    2334.78 Vancouver  Tester
06   Linda      Green      1987-JUL-30 1996-JAN-04    4322.78 New York   Tester
07   David      Larry      1990-DEC-31 1998-FEB-12    7897.78 New York   Manager
08   James      Cat        1996-SEP-17 2002-APR-15    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL>
SQL> -- Writing a DELETE Statement Containing a Subquery
SQL>
SQL> DELETE FROM employee
  2  WHERE salary >
  3    (SELECT AVG(salary)
  4     FROM employee);
4 rows deleted.
SQL>
SQL> select * from employee;
ID   FIRST_NAME LAST_NAME  START_DATE  END_DATE        SALARY CITY       DESCRIPTION
---- ---------- ---------- ----------- ----------- ---------- ---------- ---------------
01   Jason      Martin     1996-JUL-25 2006-JUL-25    1234.56 Toronto    Programmer
04   Celia      Rice       1982-OCT-24 1999-APR-21    2344.78 Vancouver  Manager
05   Robert     Black      1984-JAN-15 1998-AUG-08    2334.78 Vancouver  Tester
08   James      Cat        1996-SEP-17 2002-APR-15    1232.78 Vancouver  Tester
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>
SQL>