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23 cze 2013 · I know I'm a little late to this, but I think an easier to read solution would be to use the IF () function in MySQL: UPDATE relation. SET name1 = IF(userid1 = 3, 'jack', name1), name2 = IF(userid2 = 3, 'jack', name2) WHERE (userid1 = 3 AND userid2 = 4) OR (userid1 = 4 AND userid2 = 3);
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.
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:
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!
The format of a DATE value is 'YYYY-MM-DD'. According to standard SQL, no other format is permitted. 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';
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:
13 mar 2021 · 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 = CASE WHEN Act.Reading IS NULL THEN 0 ELSE Act.Reading - Prev.Reading ...
