在括号内匹配文本*而不是*的正则表达式

Question

I'm looking for a regex that will match all the bold text below in a PHP (PCRE) compatible pattern, this is just an example query that it needs to match, so it can't be so specific that it won't work on other similar queries.

select a.*, (select count(*) from table1 ) as t1, (select count(*) from table2 ) as t2, (select count(*) from table3 ) as t3, col1, col2 from table4 as a LEFT JOIN ( SELECT g2.*,g1.id from table5 ) as g ON ( a.id = g.id ) );

UPDATE: My idea was to match the word FROM that is not between any brackets and everything before it. The end goal is to replace all the bold text with "COUNT()" for a database abstraction layer.

Answer 1

If your question is "How can I use regexes to find the expressions that are selected at the top level of a SQL query," the short answer is, you can't.

SQL is not a "regular language" (any language that allows nesting of parentheses is not), so you're blocked right there. I believe it is a context-sensitive grammar, so you would need a separate lexical analyzer and parser.