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SQL ALTER TABLE Statement. The ALTER TABLE statement is used to add, delete, or modify columns in an existing table. The ALTER TABLE statement is also used to add and drop various constraints on an existing table.
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The ALTER TABLE statement allows you to perform the following operations on an existing table: Add a new column using the ADD clause. Modify attribute of a column such as constraint, default value, etc. using the MODIFY clause.
ALTER TABLE modifies a table definition by altering, adding, or dropping columns and constraints. ALTER TABLE also reassigns and rebuilds partitions, or disables and enables constraints and triggers.
In SQL, the ALTER TABLE command is used to modify the structure of an existing table. In this tutorial, you will learn about the SQL ALTER TABLE statement with the help of examples.
This SQL tutorial explains how to use the SQL ALTER TABLE statement to add a column, modify a column, drop a column, rename a column or rename a table (with lots of clear, concise examples). We've also added some practice exercises that you can try for yourself.
SQL - ALTER TABLE. The ALTER command is a DDL command to modify the structure of existing tables in the database by adding, modifying, renaming, or dropping columns and constraints. You can add columns, rename columns, delete columns, or change the data type of columns using the ALTER command.
4 Μαρ 2019 · Alter Table statement lets you do all this very seamlessly. With Alter Table, you can - Add, modify, or drop a column. Add or drop a constraint. You can also enable/disable constraints, but that is not in the scope of this tutorial.
