Examples of SQL analyzing

Retrieve all selected items of a SQL statement

The task here is to build a map, where the alias is the key and the expression to this alias the value of one Map entry.

Select stmt = (Select) CCJSqlParserUtil.parse("SELECT col1 AS a, col2 AS b, col3 AS c FROM table WHERE col1 = 10 AND col2 = 20 AND col3 = 30");
        
Map<String, Expression> map = new HashMap<>();        
for (SelectItem selectItem : ((PlainSelect)stmt.getSelectBody()).getSelectItems()) {
    selectItem.accept(new SelectItemVisitorAdapter() {
        @Override
        public void visit(SelectExpressionItem item) {
            map.put(item.getAlias().getName(), item.getExpression());
        }
    });
}
    
System.out.println("map " + map);

Selected items of a SQL could be of different type. We are now interested in so called SelectExpressionItems. These are those consisting of an expression optionally named by an alias. So with a SelectItemVisitor we are filtering those items. Directly from our SelectExpressionItem we can get the alias and the expression.

This will then return:

map {a=col1, b=col2, c=col3}