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Editorial Team
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Asked: 2026-06-11T03:18:00+00:00

I have a mysql table which holds lots of data across multiple tables. So

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I have a mysql table which holds lots of data across multiple tables. So to get it all out, I think the best bet is to use a UNION clause, however I also want to know which table the results come from as some have multiple values and some are null.

The following sql does not appear to work but I cant see whats wrong.

 (SELECT *, `2` AS 'cat' from `2` where `recid` = 'cneta0ld00ah')
  UNION
 (SELECT *, `3` AS 'cat' from `3` where `recid` = 'cneta0ld00ah')
  UNION
 (SELECT *, `4` AS 'cat' from `4` where `recid` = 'cneta0ld00ah')
  UNION
 (SELECT *, `5` AS 'cat' from `5` where `recid` = 'cneta0ld00ah')

All Tables look something like the following are are named, 1, 2, 3, 4 etc.

 recid         | item
 -------------------------
 cneta0ld00ah  |   1
 cneta0ld00ab  |   1
 cneta0ld00ad  |   3

I cant change the name of the tables as its an import from a very old database which we are trying to convert and extract data from.

If I run it without the ‘table-name’ AS ‘cat’, then it runs fine, as soon as I try to add in the table name it throws an error saying 

Unknown column '2' in 'field list'

It seems to be thinking 2 is a column name?

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1 Answer

  1. Editorial Team

    The problem is the backticks you have around the ‘table-name’ AS ‘cat’. Backticks are for quoting table and column names, not strings. You should use single quotes instead: 

     (SELECT *, '2' AS 'cat' from `2` where `recid` = 'cneta0ld00ah')
  UNION
 (SELECT *, '3' AS 'cat' from `3` where `recid` = 'cneta0ld00ah')
  UNION
 (SELECT *, '4' AS 'cat' from `4` where `recid` = 'cneta0ld00ah')
  UNION
 (SELECT *, '5' AS 'cat' from `5` where `recid` = 'cneta0ld00ah')
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