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1 lut 2010 · Here's a query to update a table based on a comparison of another table. If record is not found in tableB, it will update the "active" value to "n". If it's found, will set the value to NULL. UPDATE tableA LEFT JOIN tableB ON tableA.id = tableB.id SET active = IF(tableB.id IS NULL, 'n', NULL)"; Hope this helps someone else.
In this article, we would like to show you UPDATE query with IF condition in MySQL. Quick solution: UPDATE `table_name` SET `column_name` = IF(condition , if_true, if_false); Practical example. To show UPDATE query with IF condition, we will use the following users table:
13 mar 2021 · Now you can use this syntax to update all your rows in a single query: UPDATE Readings Act, LATERAL (SELECT Reading FROM Readings WHERE SystemID = Act.SystemID AND ReadingDate < Act.ReadingDate AND Reading IS NOT NULL ORDER BY SystemID, ReadingDate DESC LIMIT 1) Prev SET Act.Reading = IF(Act.Reading IS NULL, Prev.Reading, Act.Reading), Act.Diff ...
Notice the WHERE clause in the UPDATE statement. The WHERE clause specifies which record(s) that should be updated. If you omit the WHERE clause, all records in the table will be updated!
UPDATE is a DML statement that modifies rows in a table. An UPDATE statement can start with a WITH clause to define common table expressions accessible within the UPDATE. See Section 15.2.20, “WITH (Common Table Expressions)”. Single-table syntax: UPDATE [LOW_PRIORITY] [IGNORE] table_reference . SET assignment_list . [WHERE where_condition]
You should use this format in UPDATE expressions and in the WHERE clause of SELECT statements. For example: SELECT * FROM t1 WHERE date >= '2003-05-05'; As a convenience, MySQL automatically converts a date to a number if the date is used in numeric context and vice versa.
Here is an example that uses date functions. The following query selects all rows with a date_col value from within the last 30 days: mysql> SELECT something FROM tbl_name . -> WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= date_col; The query also selects rows with dates that lie in the future.
