Updating a select statement to update
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).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.If you set a column to the value it currently has, My SQL notices this and does not update it. Records not matching the equijoin from table2 are marked with null.PDF (US Ltr) - 37.9Mb PDF (A4) - 37.9Mb PDF (RPM) - 32.9Mb HTML Download (TGZ) - 8.0Mb HTML Download (Zip) - 8.1Mb HTML Download (RPM) - 6.9Mb Man Pages (TGZ) - 132.7Kb Man Pages (Zip) - 189.0Kb Info (Gzip) - 3.4Mb Info (Zip) - 3.4Mb My SQL Backup and Recovery My SQL Globalization My SQL Information Schema My SQL Installation Guide Security in My SQL Starting and Stopping My SQL My SQL and Linux/Unix My SQL and Windows My SQL and OS X Building My SQL from Source My SQL Restrictions and Limitations My SQL Partitioning My SQL Secure Deployment Guide My SQL Tutorial My SQL Performance Schema My SQL Replication Using the My SQL Yum Repository option as part of a table reference.This option takes a list of one or more partitions or subpartitions (or both).
That's how you can do ittable busstopsid | route | busstop | pos1 | 1 | A | 1 2 | 1 | B | 2 3 | 1 | C | 3 4 | 2 | C | 1 5 | 2 | D | 2 6 | 2 | A | 3 7 | 2 | E | 4 8 | 2 | F | 5 9 | 2 | G | 610 | 2 | H | 7Moving D, E, F, G To route 1 SET @pos=(SELECT max(t1.pos) FROM busstops t1 WHERE t1.route = 1 ); UPDATE busstops SET pos = ( SELECT @pos := @pos 1 ), route =1 WHERE id IN (5,7,8,9)I doubt this could be done otherwise since referencing the table you wish to update within the subquery creates circular references After DELETE or UPDATE i.e.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.I had a problem - a had to update a column "rate" but if the existince or new value is greater then 5 this "5" will be finally value in field.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.If you wish to use an increment based on subset of a table you may combine UPDATE with Variables:e.g.A table that contains entries of different categories, in which an internal order needs to represented ( lets say a table with busstops on different routes).So, I do it in one "magick" query ;)Here an example:"3" is a some value, from form or somethingupdate item set rate = case when round((rate 3)/2) You sometimes run into the problem that you want to replace a substring occuring in a column with a different string, without touching the rest of the string.The solution is surprisingly simple, thanks to My SQL: UPDATE xoops_bb_posts_text SET post_text=( REPLACE (post_text, 'morphix.sourceforge.net', ' the string function REPLACE, all items in the post_text column with 'morphix.sourceforge.net' get this substring replaced by '(Bug #11758262, Bug #50439) See Section 188.8.131.52, “Determination of Safe and Unsafe Statements in Binary Logging”, for more information.If you access a column from the table to be updated in an expression, assignments are generally evaluated from left to right.