// Extract table names from SQL statement

package main

import (
	"fmt"
	"regexp"
)

// extractTableNames from sql statement
func extractTableNames(fromSQL string) (rets []string) {
	reg := "(\\s+from\\s+(?P<table1>\\w+)\\s+((\\w+)\\s+)?(where|left|join|inner))|(\\s+join\\s+(?P<table2>\\w+)\\s+((\\w+)\\s+)?on)"
	r, _ := regexp.Compile(reg)
	n1 := r.SubexpNames()
	finds := r.FindAllStringSubmatch(fromSQL, -1)
	for _, v := range finds {
		for ii, vv := range v {
			if n1[ii] != "" && vv != "" {
				// fmt.Println("=>", n1[ii], vv)
				rets = append(rets, string(vv))
			}

		}
	}
	return
}

func main() {

	sql := `select * from Outvisit l
left join patient p on l.patid=p.patientid
join patstatic c on   l.patid=c.patid inner join patphone ph on l.patid=ph.patid
 from pharmacywestpas p where p.outvisitid=l.outvisitid)
unit all
select * from invisit where`

	fmt.Println(extractTableNames(sql))
}