What Happens If the UPDATE Subquery Returns Multiple Rows

Q

What Happens If the UPDATE Subquery Returns Multiple Rows? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements

✍: FYIcenter.com

A

If a subquery is used in a UPDATE statement, it must return exactly one row for each row in the update table that matches the WHERE clause. If it returns multiple rows, MySQL server will give you an error message. To test this out, you can try the following tutorial exercise:

mysql> INSERT INTO fyi_rates VALUES (0, 'Number 1');
Query OK, 1 row affected (0.00 sec)

mysql> INSERT INTO fyi_rates VALUES (0, 'Number 2');
Query OK, 1 row affected (0.00 sec)

mysql> SELECT * FROM fyi_rates WHERE id = 0;
+------+----------+
| id   | comment  |
+------+----------+
|    0 | Number 1 |
|    0 | Number 2 |
+------+----------+
2 rows in set (0.00 sec)

mysql> UPDATE fyi_links SET notes = (
    SELECT comment FROM fyi_rates 
    WHERE fyi_rates.id = fyi_links.id
   ) 
   WHERE id = 0;
ERROR 1242 (21000): Subquery returns more than 1 row

2007-05-11, 5085👍, 0💬

What Happens If the UPDATE Subquery Returns No Rows
What Happens If the UPDATE Subquery Returns No Rows? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you use a subquery to assign new values in the SET clause in an UPDATE statement, and the subquery returns no rows for an outer row, MySQL will provide a NULL value to the SE... 2007-05-11, 5150👍, 0💬

What Happens If the UPDATE Subquery Returns Multiple Rows
What Happens If the UPDATE Subquery Returns Multiple Rows? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If a subquery is used in a UPDATE statement, it must return exactly one row for each row in the update table that matches the WHERE clause. If it returns multiple rows, My... 2007-05-11, 5086👍, 0💬

How To Use Existing Values in UPDATE Statements
How To Use Existing Values in UPDATE Statements? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If a row matches the WHERE clause in a UPDATE statement, existing values in this row can be used in expressions to provide new values in the SET clause. Existing values are represen... 2007-05-11, 4998👍, 0💬

How To Use Values from Other Tables in UPDATE Statements
How To Use Values from Other Tables in UPDATE Statements? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you want to update values in one table with values from another table, you can use a subquery as an expression in the SET clause. The subquery should return only one row... 2007-05-11, 4900👍, 0💬

Is the Order of Columns in the SET Clause Important
Is the Order of Columns in the SET Clause Important? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements Yes. The order of columns in the SET clause of the UPDATE statement is important. There is a BIG DIFFERENCE between MySQL and Oracle on update columns with previous values: Orac... 2007-05-11, 4891👍, 0💬

How To Create a Testing Table with Test Data
How To Create a Testing Table with Test Data? - MySQL FAQs - SQL SELECT Query Statements with GROUP BY If you want to follow the tutorial exercises presented in this collection, you need to create a testing table and insert some test data, as shown in the following sample script: mysql> CREATE TABLE... 2007-05-11, 4877👍, 0💬

How To Update Values on Multiple Rows
How To Update Values on Multiple Rows? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If the WHERE clause in an UPDATE matches multiple rows, the SET clause will be applied to all matched rows. This rule allows you to update values on multiple rows in a single UPDATE statement... 2007-05-11, 4873👍, 0💬

How To Delete Multiple Rows from a Table
How To Delete Multiple Rows from a Table? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements You can delete multiple rows from a table in the same way as deleting a single row, except that the WHERE clause will match multiple rows. The tutorial exercise below deletes 3 rows from t... 2007-05-11, 4850👍, 0💬

How To Delete an Existing Row from a Table
How To Delete an Existing Row from a Table? - MySQL FAQs - Understanding SQL INSERT, UPDATE and DELETE Statements If you want to delete an existing row from a table, you can use the DELETE statement with a WHERE clause to identify that row. Here is good sample of DELETE statements: mysql> INSERT INT... 2007-05-11, 4774👍, 0💬

All rights in the contents of this web site are reserved by the individual author. fyicenter.com does not guarantee the truthfulness, accuracy, or reliability of any contents.