SQL queries to alter the table structure.

Add Column

ALTER TABLE TableName
ADD FieldName varchar(255);

Drop Column

ALTER TABLE TableName
DROP COLUMN FieldName;

Rename column

ALTER TABLE TableName
RENAME COLUMN OldName to NewName;

Add Primary Key

ALTER TABLE TableName
ADD PRIMARY KEY (Column);

Alter/Change column data type

ALTER TABLE TableName
ALTER COLUMN ColumnName varchar(255);

Alter/Change column data type with PK

ALTER TABLE TableName DROP CONSTRAINT PK_Name
ALTER TABLE TableName ALTER COLUMN ColumnName varchar(11) NOT NULL;
ALTER TABLE TableName ADD CONSTRAINT PK_NamePRIMARY KEY (ColumnName);
Source
https://www.w3schools.com/SQl/sql_alter.asp

Categorized in:

SQL,

Last Update: November 28, 2025