terrymanu commented on issue #18763:
URL:
https://github.com/apache/shardingsphere/issues/18763#issuecomment-3636751520
## Issue Understanding
- On ShardingSphere-Proxy 5.1.2 (read/write splitting only, MySQL driver
8.0.28) a SELECT fails with This version of ShardingSphere-Proxy doesn't yet
support this SQL. 'You have an error in your SQL syntax'.
- SQL shown: SELECT knowledgename, knowledgecontent FROM Academic WHERE
knowledgename LIKE "%"? "%"; user says direct MySQL seems fine.
## Root Cause
- The SQL is syntactically invalid: LIKE "%"? "%" puts % as string
literals and inserts ? between them, which is not valid SQL. The parser
therefore throws a syntax error.
- Per ShardingSphere usage, wildcard characters for LIKE must come from
the parameter value itself or be concatenated in SQL, not written as "%"? "%".
## Analysis
- Same pattern as #17888: a SQL syntax error, not a missing Proxy feature.
- Correct forms:
- WHERE knowledgename LIKE CONCAT('%', ?, '%') (parameter without %),
or
- WHERE knowledgename LIKE ? with the parameter value %keyword%.
- Read/write splitting routing does not affect syntax; the same prepared
SQL sent directly to MySQL would also fail.
## Conclusion
- This is a SQL writing issue, not a ShardingSphere bug.
- Fix the mapper LIKE clause to a standard prepared form (parameter
carries %, or use CONCAT/CONCAT_WS to add wildcards) and avoid the "%"? "%"
pattern.
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