In this tutorial, we have shown you how to use the SQL UPDATE statement to modify existing data in a table. ![]() In the SET clause, instead of using the literal values, we used a subquery to get the corresponding last name value from the employees table. ) Code language: SQL (Structured Query Language) ( sql )īecause the WHERE clause is omitted, the UPDATE statement updated all rows in the dependents table. To make sure that the last names of children are always matched with the last name of parents in the employees table, you use the following statement: UPDATE dependents Sometimes when employees change their last names, you update the employees table only without updating the dependents table. To update the last names of Nancy’s dependents, you use the following UPDATE statement. In this case, you need to update all Nancy’s dependents in the dependents table.īefore updating the data, let’s check the dependents of Nancy. SQL ALTER TABLE Statement In SQL, the ALTER TABLE command is used to modify the structure of an existing table like adding, deleting, renaming columns, etc. Now, Nancy wants to change all her children’s last names from Bell to Lopez. You can verify it by using the following SELECT statement. The database system updated value in the last_name column and the row with employee_id 192. To update Sarah’s last name from Bell to Lopez, you use the following UPDATE statement: UPDATE employeesĮmployee_id = 192 Code language: SQL (Structured Query Language) ( sql ) Suppose the employee id 192 Sarah Bell changed her last name from Bell to Lopez and you need to update her record in the employees table. We will use the employees and dependents table to demonstrate the UPDATE statement. Because the WHERE clause is optional, therefore, if you omit it, the all the rows in the table will be affected. However, any row that causes the condition in the WHERE to evaluate to true will be modified. For example, if the WHERE clause contains a primary key expression, the UPDATE statement changes one row only. The UPDATE statement affects one or more rows in a table based on the condition in the WHERE clause.
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