Primary key

Change primary key sql

ALTER TABLE <Table_Name>
DROP CONSTRAINT <constraint_name>

ALTER TABLE <Table_Name>
ADD CONSTRAINT <constraint_name> PRIMARY KEY (<Column1>,<Column2>)

Source: stackoverflow.com

What is primary key

PRIMARY KEY  -- unique identifier for the entire row of record in a table 
             -- can not be null and must be unique

Primary key

CREATE TABLE Persons (
    Rollno int NOT NULL,
    FirstName varchar(255),
    LastName varchar(255),
    Age int,
    PRIMARY KEY (ID)
);

Source: computerscienceai.com

Primary key

Primary Key :
It is unique column in every table in a database
It can ONLY accept;
    - nonduplicate values
    - cannot be NULL

Primary key

CREATE TABLE purchase_orders (
    po_nr NUMBER,
    vendor_id NUMBER NOT NULL,
    po_status NUMBER(1,0) NOT NULL,
    created_at TIMESTAMP WITH TIME ZONE NOT NULL,
    CONSTRAINT pk_purchase_orders PRIMARY KEY(po_nr)
);

Source: datawitzz.com

Similar codes

3 votes197 views1 answer
Null sql
SQL
22 votes195 views4 answers
Show list of users in mysql
SQL
0 vote186 views2 answers
Mysql two column combination unique
SQL
0 vote200 views4 answers
Change schema in sql server
SQL
0 vote201 views1 answer
Automatically update database last seen datetime in sql
SQL
0 vote197 views1 answer
Select other columns with distinct
SQL
0 vote272 views1 answer
Grant privileges mysql to database 1064
SQL
0 vote184 views1 answer
Remove default constraint sql server
SQL
11 votes247 views2 answers
Mysql disable safe mode
SQL
0 vote214 views1 answer
Mysql begin statement
SQL