How to use update statement in SQL

In SQL, the UPDATE statement is used to modify a specific column or row of an existing record in a table. Its syntax is as follows: UPDATE table_nameSET column1 = value1, column2 = value2, ...WHERE condition;

Usage of UPDATE statements in SQL

The UPDATE statement is used in SQL to update existing records in tables. It allows modifying specific columns or rows of existing data.

grammar

 <code class="sql">UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;</code>

parameter

• table_name: The table name to be updated.
• column1, column2, ...: The column name to be updated.
• value1, value2, ...: The new value to be set.
• WHERE condition: Optional condition, used to update only rows that meet the specified conditions.

usage

1. Update a single column:

 <code class="sql">UPDATE students SET name = 'John Smith' WHERE id = 1;</code>

2. Update multiple columns:

 <code class="sql">UPDATE students SET name = 'John Smith', age = 25 WHERE id = 1;</code>

3. Updated using conditions:

 <code class="sql">UPDATE students SET name = 'John Smith' WHERE id = 1 AND age > 20;</code>

4. Update all rows:

 <code class="sql">UPDATE students SET name = 'John Smith';</code>

Things to note

• The UPDATE statement only updates rows that meet the WHERE conditions.
• The WHERE condition is optional and if not specified, it will update all rows in the table.
• If the updated value is the same as the existing value, no changes are made.
• The UPDATE statement does not return the updated number of rows. To get the updated number of rows, use the @@ROWCOUNT system variable.

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