Commands to modify structure in sql

Commands to modify the table structure in SQL include ALTER TABLE (add/delete/modify columns, rename tables), ADD COLUMN (add columns), DROP COLUMN (delete columns), MODIFY COLUMN (modify column data types ), CREATE INDEX (create index), DROP INDEX (delete index).

Structure modification commands in SQL

In SQL, there are many commands that can be used to modify the table structure. These commands can be used to add or remove columns, change data types, or create indexes. The most commonly used structure modification commands include:

• ALTER TABLE: used to add, delete or modify columns, and change table names.
• ADD COLUMN: Add a new column to the table.
• DROP COLUMN: Delete a column from the table.
• MODIFY COLUMN: Change the data type, size, or constraints of a column.
• ALTER TABLE RENAME: Rename the table to a new name.
• CREATE INDEX: Create an index on the table to improve query performance.
• DROP INDEX: Delete the index from the table.

Example:

To add a new column named email to table customers, you can Use the following command:

<code class="sql">ALTER TABLE customers ADD COLUMN email VARCHAR(255) NOT NULL;</code>

To delete the product_id column from table orders, you can use the following command:

<code class="sql">ALTER TABLE orders DROP COLUMN product_id;</code>

To alter table The data type of the price column in products is floating point. You can use the following commands:

<code class="sql">ALTER TABLE products MODIFY COLUMN price DECIMAL(10, 2);</code>

These commands provide a powerful way to flexibly modify the table structure, allowing you to The database schema needs to be adjusted.

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