SQL UPDATE with LIKE

Question

I was trying to update approx 20,000 records in a table by using statements like this one, however, I got the message say 0 row(s) affected so it didn\'t work.<

Answer 1

By default MySQL allows double quoted names to be understood as either identifiers (like column names) or as string literals.

This is meant as a convenience, but I find the semantic ambiguity frustrating. MySQL must resolve the ambiguity, and cannot magically always guess the coder's intention, as you discovered.

-- In default sql_mode under 5.5
--
SELECT "foo"           -- "foo" is a *column* if tbl.foo exists, otherwise a string 
  FROM "tbl"           -- Oops!  ER_PARSE_ERROR (1064)  Can't do this in default mode.
 WHERE "foo" = "foo";  -- Both of these are strings

So, the way around it is to force unambiguous interpretation of identifiers:

1. Do not quote simple identifiers
2. Use MySQL-specific backticks for quoting
   (This is ODBC's SQL_IDENTIFIER_QUOTE_CHAR)
3. Always override the change the sql_mode to include ANSI_QUOTES (or a superset of it)
   Double quotes are then exclusively for identifiers, single quotes for strings.

#3 is my personal favorite, for readability and portability. The problem is it tends to surprise people who only know MySQL, and you have to remember to override the default.