Updating trigger mysql
If you do not use it, all rows that are outside the range of your updated values will be set to blank!
If you wish to use an increment based on subset of a table you may combine UPDATE with Variables:e.g.
So, here it is again.]A very server resources friendly method to update multiple rows in the same table is by using WHEN THEN (with a very important note).
UPDATE tbl_name SET fld2 = CASE fld1WHEN val1 THEN data1WHEN val2 THEN data2ELSE fld2 ENDThe note is: do not forget ELSE.
This option takes a list of one or more partitions or subpartitions (or both).
Only the partitions (or subpartitions) listed are checked for matches, and a row that is not in any of these partitions or subpartitions is not updated, whether it satisfies the clause, are flagged as unsafe for statement-based replication.
Notes: That index addition is necessary because on larger tables my SQL would rather die than figure to (internally) index a single column join.
I was not able, using my SQL 4.1.1, to do this as a subquery: UPDATE Groups LEFT JOIN (SELECT Group Id, MIN(Val Within Group) AS base Val FROM Groups GROUP BY Group Id) AS Grp Sum USING (Group Id) SET Val Within Group=Val Within Group-base Val; Csaba Gabor UPDATE Syntax with "on-line" updating value limitations.
Ideal when writing a script is just too much effort.
Here is a way to use multiple tables in your UPDATE statement, but actually copying one row values into the other, meaning, we're using the same table: UPDATE jobs AS to Table, jobs AS from Table SET to Table.job_type_id = from Table.job_type_id, to Table.job_company_id = from Table.job_company_id, to Table.job_source = from Table.job_source, WHERE (to Table.job_id = 6) AND (from Table.job_id = 1)--------------Pretty cool.
What I'm doing here is copying the information I need from the row where job_id=1 to the row where job_id=6, on the same table.
If you access a column from the table to be updated in an expression, assignments are generally evaluated from left to right.
For multiple-table updates, there is no guarantee that assignments are carried out in any particular order. COLUMN2 IS NULLAn outerjoin is performed based on the equijoin condition.