| Bug #29326 | comparisons using row constructors throw collation erro | ||
|---|---|---|---|
| Submitted: | 24 Jun 2007 23:46 | Modified: | 19 Dec 2008 8:09 |
| Reporter: | Peter Brawley (Basic Quality Contributor) | Email Updates: | |
| Status: | Duplicate | Impact on me: | |
| Category: | MySQL Server: Charsets | Severity: | S3 (Non-critical) |
| Version: | 5.0.40, 5.1.19 | OS: | Any |
| Assigned to: | Assigned Account | CPU Architecture: | Any |
| Tags: | qc | ||
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Description: This succeeds: select * from mysql.user where host='localhost' and user='test'; but this ... select * from mysql.user where (host,user) = ('localhost','test'); fails with ERROR 1267 (HY000): Illegal mix of collations (utf8_bin,IMPLICIT) and (latin1_swedish_ci,COERCIBLE) for operation '='. What user can be expected, reasonably, to anticipate that her mysql database, as it was delivered with her copy of MySQL, defaults to collation-incompatibility with the mysql client software delivered with her database!? Sec. 13.2.8.5. of the manual says flatly: "SELECT * FROM t1 WHERE (1,2) = (SELECT column1, column2 FROM t2); SELECT * FROM t1 WHERE ROW(1,2) = (SELECT column1, column2 FROM t2); The queries here are both TRUE if table t2 has a row where column1 = 1 and column2 = 2." Nothing in the manual suggests that a comparison of (col1, col2) with (val1, val2) will fail where scalar comparisons of the same columns and values succeeds. So is it a documentation error or a server error? Looks like the latter. How to repeat: As above Suggested fix: Avoid row constructors in comparison clauses, a serious drawback for writing general purpose queries. A drawback which ought not to be there.