SQL > SQL ALTER TABLE > Modify Column Syntax

Sometimes we need to change the data type of a column. To do this, we use the ALTER TABLE Modify Column command. For Oracle and MySQL, the SQL syntax for ALTER TABLE Modify Column is,

ALTER TABLE "table_name"
MODIFY "column_name" "New Data Type";

For SQL Server, the syntax is,

ALTER TABLE "table_name"
ALTER COLUMN "column_name" "New Data Type";

Let's look at the example. Assuming our starting point is the Customer table created in the CREATE TABLE section:

Table Customer

Column NameData Type
First_Namechar(50)
Last_Namechar(50)
Addresschar(50)
Citychar(50)
Countrychar(25)
Birth_Datedatetime

Our goal is to alter the data type of the "Address" column to char(100). To do this, we key in:

MySQL:

ALTER TABLE Customer MODIFY Address char(100);

Oracle:

ALTER TABLE Customer MODIFY Address char(100);

SQL Server:

ALTER TABLE Customer ALTER COLUMN Address char(100);

Resulting table structure:

Table Customer

Column NameData Type
First_Namechar(50)
Last_Namechar(50)
Addresschar(100)
Citychar(50)
Countrychar(25)
Birth_Datedatetime

Next: SQL RENAME COLUMN




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