Create a primary key (example)

Create a primary key (example)

SQL> alter table emp_ogg add constraint PK_empno primary key (empno );

-- Create a primary key

Queries the constraints of a table.

SQL> desc user_constraints;
 
Name Null? Type
-----------------------------------------------------------------------------
OWNER VARCHAR2 (30)
CONSTRAINT_NAME not null VARCHAR2 (30)
CONSTRAINT_TYPE VARCHAR2 (1)
TABLE_NAME not null VARCHAR2 (30)
SEARCH_CONDITION LONG
R_OWNER VARCHAR2 (30)
R_CONSTRAINT_NAME VARCHAR2 (30)
DELETE_RULE VARCHAR2 (9)
STATUS VARCHAR2 (8)
DEFERRABLE VARCHAR2 (14)
DEFERRED VARCHAR2 (9)
VALIDATED VARCHAR2 (13)
GENERATED VARCHAR2 (14)
BAD VARCHAR2 (3)
RELY VARCHAR2 (4)
LAST_CHANGE DATE
INDEX_OWNER VARCHAR2 (30)
INDEX_NAME VARCHAR2 (30)
INVALID VARCHAR2 (7)
VIEW_RELATED VARCHAR2 (14)

SQL> select CONSTRAINT_NAME, INDEX_NAME, TABLE_NAME from user_constraints;

-- Query constraints for a user

-- Check whether a primary key exists.

CONSTRAINT_NAME INDEX_NAME TABLE_NAME
------------------------------------------------------------------------------------------
PK_DEPT DEPT
PK_EMP EMP
FK_DEPTNO EMP
SYS_C0010809 SYS_C0010809 TCUSTMER
Sys_c00000010 sys_c00000010 TCUSTORD