SQL DEFAULT CONSTRAINT
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SQL DEFAULT Constraint
The DEFAULT constraint is used to insert a default value into a column.
The default value will be added to all new records, if no other value is specified.
SQL DEFAULT Constraint on CREATE TABLE
The following SQL creates a DEFAULT constraint on the "City" column when the "Persons" table is created:My SQL / SQL Server / Oracle / MS Access:
CREATE TABLE Persons
( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255) DEFAULT 'Sandnes' ) |
CREATE TABLE Orders
( O_Id int NOT NULL, OrderNo int NOT NULL, P_Id int, OrderDate date DEFAULT GETDATE() ) |
SQL DEFAULT Constraint on ALTER TABLE
To create a DEFAULT constraint on the "City" column when the table is already created, use the following SQL:MySQL:
ALTER TABLE Persons
ALTER City SET DEFAULT 'SANDNES' |
ALTER TABLE Persons
ALTER COLUMN City SET DEFAULT 'SANDNES' |
To DROP a DEFAULT Constraint
To drop a DEFAULT constraint, use the following SQL:MySQL:
ALTER TABLE Persons
ALTER City DROP DEFAULT |
ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT |
This post was written by: Rajendra Prasad
Rajendra Prasad is a professional blogger, web designer and front end web developer. Follow him on Facebook
