Rewriting updating maintenance procedures5 | | -------- -------------------------------------------- Update column in a table whose values are not found in another table. Many server admins default the My SQL daemon to 'safe mode'.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.Adam Boyle's commment above was just what I was trying to do, update one table based on a relationship between that table and another.PDF (US Ltr) - 31.1Mb PDF (A4) - 31.2Mb PDF (RPM) - 29.4Mb HTML Download (TGZ) - 7.2Mb HTML Download (Zip) - 7.2Mb HTML Download (RPM) - 6.2Mb Man Pages (TGZ) - 177.1Kb Man Pages (Zip) - 287.4Kb Info (Gzip) - 3.0Mb Info (Zip) - 3.0Mb My SQL Backup and Recovery My SQL Globalization My SQL Information Schema My SQL Installation Guide My SQL and Linux/Unix My SQL and OS X My SQL Partitioning My SQL Performance Schema My SQL Replication Using the My SQL Yum Repository My SQL Restrictions and Limitations Security in My SQL My SQL and Solaris Building My SQL from Source Starting and Stopping My SQL My SQL Tutorial My SQL and Windows My SQL NDB Cluster 7.3-7.4 option as part of a table reference.This option takes a list of one or more partitions or subpartitions (or both).
The @value := col will always evaluate to true and will store the col value before the update in the @value variable.
Ideal when writing a script is just too much effort.
Sometimes you have a lot of processes that could be updating a column value in a table. ID=54321 Here's a workaround for the update/subquery/cant do self table "bug"Senario is, ID 8 has multiple records, only the last (highest) record needs to be changedupdate t1 set c1 = ' NO'where id='8'order by recno desc limit 1I would prefer update t1 set c1=' NO' WHERE ID=8 AND RECNO = (SELECT MAX(RECNO) FROM T1 WHERE ID=8)But that's not currently allowed If you want to update a table based on an aggregate function applied to another table, you can use a correlated subquery, for example: UPDATE table1 SET table1field = (SELECT MAX(table2.table2field) FROM table2 WHERE table1.table1field = table2.table2field)This can be helpful if you need to create a temporary table storing an ID (for, say, a person) and a "last date" and already have another table storing all dates (for example, all dates of that person's orders).
[I have posted this in the Flow Control Functions page last year but I still see people asking how to update multiple rows.
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).