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

1 vote146 views1 answer
Mysql select update same table
SQL
2 votes108 views1 answer
Sql select min value from multiple columns
SQL
0 vote151 views1 answer
Sql query for displaying age from oldest to youngest
SQL
0 vote148 views1 answer
Group by two columns postgres
SQL
0 vote153 views1 answer
The report definition has an invalid target namespace 'http://schemas.microsoft.com/SQLServer/reporting/reportdesigner'
SQL
0 vote150 views1 answer
Enable Rabbitmq management plugin
SQL
16 votes141 views1 answer
Mysql mediumint max value
SQL
2 votes143 views6 answers
In in sql
SQL
3 votes143 views2 answers
Update Query in SQL Server
SQL
0 vote183 views1 answer
Month mysql
SQL