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A is a normal table, B is a temporary table: Worked in 4update A, B set A.population=B.pop_count where A.id=In version 5, however, the above query only updated one element while still matching "all"In 5 I had to do it like this:update A RIGHT JOIN B on A.id=set A.population=B.pop_count Updates all population counts correctly.[edit: RIGHT JOIN not LEFT JOIN...] Related to the post of Mohamed Hossam on May 9 2005 am A more general method to updtate more one row: UPDATE table SET f1='foo', f2= IF(f3=value,‘one’, IF(f3=value_bis,’two’,f2)) WHERE f5='afected' This set the values of field 'f2' according to the values of field 'f3' in the rows field f5 'afected'.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.
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).
If you update a column that has been declared , an error occurs if strict SQL mode is enabled; otherwise, the column is set to the implicit default value for the column data type and the warning count is incremented. This facilitates to update table1 column with expression whose corresponding value from table2 is returned as NULL It took me a few minutes to figure this out, but the syntax for UPDATING ONE TABLE ONLY using a relationship between two tables in My SQL 4.0 is actually quite simple:update t1, t2 set t1.field = t2.value where t1= t2.that; It should be noted that even simple applications of UPDATE can conflict with the 'safe mode' setting of the mysql daemon.
The implicit default value is tables for which there are foreign key constraints, the My SQL optimizer might process tables in an order that differs from that of their parent/child relationship. Instead, update a single table and rely on the PDF (US Ltr) - 38.0Mb PDF (A4) - 38.0Mb PDF (RPM) - 36.6Mb HTML Download (TGZ) - 9.9Mb HTML Download (Zip) - 9.9Mb HTML Download (RPM) - 8.7Mb Man Pages (TGZ) - 207.1Kb Man Pages (Zip) - 315.5Kb Info (Gzip) - 3.5Mb Info (Zip) - 3.5Mb 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 7.5 My SQL Secure Deployment Guide I will update field text in table Awith UPDATE `Table A`,`Table B`SET `Table A`.`text`=concat_ws('',`Table A`.`text`,`Table B`.`B-num`," from ",`Table B`.`date`,'/')WHERE `Table A`.`A-num` = `Table B`.`A-num`and come to this result Table A -------- -------------------------------------------- | A-num | text | | 1 | 24 from 03 08 2003 || 2 | 22 from 01 08 2003 / 23 from 02 08 2003 / | | 3 | || 4 | 25 from 04 08 2003 / 26 from 05 03 2003 / || 5 | | -------- -------------------------------------------- Update column in a table whose values are not found in another table. Many server admins default the My SQL daemon to 'safe mode'.
If you want to return the value before you updated it without using a seperate select (which unless you lock the table could return a different value than is updated) then you can use a mysql variable like this:update some_table set col = col 1 where key = 'some_key_value' and @value := col The @value := col will always evaluate to true and will store the col value before the update in the @value variable. Additional information on My SQL correlated subqueries is at UPDATE can apparently be used to implement a semaphore (pardon my pseudocode):while TRUE The code above waits until the semaphore is "cleared" (value = 0) and then "sets" it (value = 1).