Oracle PL/SQL/Constraints/Drop Constraint — различия между версиями
Admin (обсуждение | вклад) м (1 версия) |
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(нет различий)
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Версия 13:45, 26 мая 2010
Alter table to drop constraint with name
SQL> --Unique Key
SQL>
SQL>
SQL> create table myTable (
2 a number unique,
3 b number
4 );
Table created.
SQL>
SQL>
SQL> desc
Usage: DESCRIBE [schema.]object[@db_link]
SQL>
SQL> insert into myTable values (4, 5);
1 row created.
SQL> insert into myTable values (2, 1);
1 row created.
SQL> insert into myTable values (2, 1);
insert into myTable values (2, 1)
*
ERROR at line 1:
ORA-00001: unique constraint (SYS.SYS_C004357) violated
SQL> insert into myTable values (9, 8);
1 row created.
SQL> insert into myTable values (6, 9);
1 row created.
SQL> insert into myTable values (null,9);
1 row created.
SQL> insert into myTable values (null,9);
1 row created.
SQL>
SQL> select * from myTable;
A B
---------- ----------
4 5
2 1
9 8
6 9
9
9
6 rows selected.
SQL>
SQL> alter table myTable drop constraint sys_c004357;
Table altered.
SQL>
SQL>
SQL> insert into myTable values (4, 5);
1 row created.
SQL> insert into myTable values (2, 1);
1 row created.
SQL> insert into myTable values (2, 1);
1 row created.
SQL> insert into myTable values (9, 8);
1 row created.
SQL> insert into myTable values (6, 9);
1 row created.
SQL> insert into myTable values (null,9);
1 row created.
SQL> insert into myTable values (null,9);
1 row created.
SQL>
SQL> select * from myTable;
A B
---------- ----------
4 5
2 1
9 8
6 9
9
9
4 5
2 1
2 1
9 8
6 9
A B
---------- ----------
9
9
13 rows selected.
SQL>
SQL> drop table myTable;
Drop a UNIQUE constraint without specifying its name by referencing the column or columns
SQL> -- create demo table
SQL> create table Employee(
2 ID VARCHAR2(4 BYTE) unique,
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> -- Drop a UNIQUE constraint without specifying its name by referencing the column or columns.
SQL>
SQL> ALTER TABLE Employee DROP UNIQUE (id);
Table altered.
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
2 /
Table dropped.
SQL>
SQL>
SQL>
Drop Unique Constraint and Add Primary Key
SQL>
SQL> CREATE TABLE myTable (
2 Name VARCHAR(50) NOT NULL,
3 PhoneNo VARCHAR(15),
4 CONSTRAINT unq_name UNIQUE(Name));
Table created.
SQL>
SQL> ALTER TABLE myTable DROP CONSTRAINT unq_name;
Table altered.
SQL> ALTER TABLE myTable ADD CONSTRAINT PK_myTableName PRIMARY KEY (Name);
Table altered.
SQL>
SQL>
SQL> drop table myTable;
Table dropped.