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What is ALTER TABLE?
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What is an 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. ALTER TABLE - ADD Column. To add a column in a table, use the following syntax: ALTER TABLE table_name. ADD column_name datatype;
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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. Important. The syntax for ALTER TABLE is different for disk-based tables and memory-optimized tables.
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. Remove columns using the DROP clause. We will examine each operation in detail in the following sections.
An ALTER TABLE statement is part of DDL, and is for altering a table schema only; we'll look at updating data in a table later in this book. The basic format of an ALTER TABLE statement is: ALTER TABLE table_to_change. stuff_to_change_goes_here. additional_arguments.
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. Add Columns in the Table.
ALTER TABLE. Purpose. Use the ALTER TABLE statement to alter the definition of a nonpartitioned table, a partitioned table, a table partition, or a table subpartition. For object tables or relational tables with object columns, use ALTER TABLE to convert the table to the latest definition of its referenced type after the type has been altered.
In SQL, the ALTER TABLE command is used to modify the structure of an existing table like adding, deleting, renaming columns, etc. Example. -- add phone column to Customers table ALTER TABLE Customers. ADD phone varchar(10); Run Code. Here, the SQL command adds a column named phone to the Customers table. ALTER TABLE Syntax.
