How to add multiple new columns in SQL

Methods to add multiple new columns in SQL include: Using the ALTER TABLE statement: ALTER TABLE table_name ADD column1 data_type, ADD column2 data_type, ...; Using the CREATE TABLE statement: CREATE TABLE new_table AS SELECT column1, column2, ..., columnn FROM existing_table UNION ALL SELECT NULL, NULL, ..., NUL

How to add multiple new columns in SQL

Introduction
Adding new columns in SQL tables is a common operation to extend data structures and store more complex data. There are multiple ways to add multiple new columns.

method

1. Use the ALTER TABLE statement

 <code class="sql">ALTER TABLE table_name ADD column1 data_type, ADD column2 data_type, ... ADD columnn data_type;</code>

• Replace table_name with the table name you want to add new columns.
• For each new column to add, specify column_name and data_type .
• Use commas to separate multiple added new columns.

2. Use CREATE TABLE statement

 <code class="sql">CREATE TABLE new_table AS SELECT column1, column2, ..., columnn FROM existing_table UNION ALL SELECT NULL, NULL, ..., NULL;</code>

• Use existing_table as the base table to add new columns.
• Specifies the name and data type of the new column.
• UNION ALL operator is used to merge two tables and add new columns to existing data.

example

To add age and salary columns to the employees table, you can use the following statement:

 <code class="sql">ALTER TABLE employees ADD age INT, ADD salary DECIMAL(10,2);</code>

Things to note

• Make sure the data type of the new column you added matches the expected data.
• If the existing data is incompatible with the data type of the new column, data may be lost.
• Before adding new columns, it is best to back up the table to prevent data loss.

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