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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.
16 kwi 2016 · However, given how the conditions are re-used in your UPDATE statement, you could also take a different approach altogether: represent the affected IDs and the new values as a derived table and use an update with a join:
The MySQL UPDATE Statement. The UPDATE statement is used to modify the existing records in a table. UPDATE Syntax. UPDATE table_name. SET column1 = value1, column2 = value2, ... WHERE condition; Note: Be careful when updating records in a table! Notice the . WHERE clause in the UPDATE statement.
The WHERE clause, if given, specifies the conditions that identify which rows to update. With no WHERE clause, all rows are updated. If the ORDER BY clause is specified, the rows are updated in the order that is specified. The LIMIT clause places a limit on the number of rows that can be updated.
If you want to change the field to 'hello' only if it is 'bye', use this: UPDATE table1 SET col1 = 'hello' WHERE col1 = 'bye' If you want to update only if it is different that 'hello', use: UPDATE table1 SET col1 = 'hello' WHERE col1 <> 'hello' Is there a reason for this strange approach?
The WHERE clause, if given, specifies the conditions that identify which rows to update. With no WHERE clause, all rows are updated. If the ORDER BY clause is specified, the rows are updated in the order that is specified. The LIMIT clause places a limit on the number of rows that can be updated.
24 lip 2024 · The UPDATE statement requires you to update data in a table that already exists and for a row that already exists. The basic syntax of the statement is: UPDATE table_name. SET column1 = value1, column2 = value2, …. WHERE condition;
