vitess sql parser to get a list of columns a query will generate

main.go

package main

import (
	"errors"
	"fmt"
	"log"

	"github.com/youtube/vitess/go/vt/sqlparser"
)

func columnNames(sql string) ([]string, error) {
	cn := []string{}
	stmt, err := sqlparser.Parse(sql)
	if err != nil {
		return cn, err
	}
	s, ok := stmt.(*sqlparser.Select)
	if !ok {
		return cn, errors.New("expected select statement for given sql")
	}
	for _, expr := range s.SelectExprs {
		nse, ok := expr.(*sqlparser.NonStarExpr)
		if !ok {
			return cn, errors.New("unhandled select expression type")
		}
		// if there is an As, we don't care what type it is, we'll use that as the column name
		if len(nse.As) > 0 {
			cn = append(cn, string(nse.As))
			continue
		}
		// if there was no AS, we only accept ColName types as our value, other types are invalid
		col, ok := nse.Expr.(*sqlparser.ColName)
		if !ok {
			return cn, errors.New("select expression is not column name and has no AS clause")
		}
		cn = append(cn, string(col.Name))
	}
	return cn, nil
}

func main() {
	cn, err := columnNames("select (select * from feef) as lulz, poop as feef, count(*) as fish, jerks from (select ass from jerks)")
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%v\n", cn)
}