Describe the bug
jsqlparser cannot parse the expression with "=" in select statement.
To Reproduce
Steps to reproduce the behavior:

1. Example SQL select sum(case when companyid not in (null) then 1 else 0 end)=1 as validate_companyid from table1;

2. Parsing this SQL using JSqlParser with this statements
   CCJSqlParserManager ccjSqlParserManager = new CCJSqlParserManager();
   Statement statement;
   List columns = new ArrayList();
   try {
   statement = ccjSqlParserManager.parse(new StringReader(singleSql));

3. Exception
   Caused by: net.sf.jsqlparser.parser.ParseException: Encountered unexpected token: "=" "="
   at line 1, column 64.
   Was expecting one of:

   "&"
   ","
   "."
   "::"
   ";"
   "<<"
   ">>"
   ...
   Expected behavior

System

• Database you are using postgres
• Java Version 1.8_222
• JSqlParser version 3.1