Function LeftJoinSqlBuild

models/Models.go:399–441

左联合查询创建SQL语句 @param tables 需要作为联合查询的数据表。注意：数据表的第一个表是主表 @param on 联合查询的on查询条件，必须必表(tables)少一个。比如user表和user_info表做联合查询，那么on查询条件只有一个，必tables的数组元素少一个 @param fields 需要查询的字段 @param p

(tables []string, on []map[string]string, fields map[string][]string, p, listRows int, orderBy []string, groupBy []string, condition string)

//sql, err := LeftJoinSqlBuild(tables, on, fields, 1, 100, orderby, nil, "")
//fmt.Println(sql, err)
func LeftJoinSqlBuild(tables []string, on []map[string]string, fields map[string][]string, p, listRows int, orderBy []string, groupBy []string, condition string) (sql string, err error) {
	if len(tables) < 2 || len(tables)-1 != len(on) {
		err = errors.New("参数不规范：联合查询的数据表数量必须在2个或2个以上，同时表数量比on条件多一个")
		return
	}
	var (
		FieldSlice   []string
		StrOrderBy   string
		StrGroupBy   string
		StrCondition string
		joinKV       string
		join         = []string{tables[0]}
		usedTables   = []string{}
	)
	for table, field := range fields {
		for _, f := range field {
			FieldSlice = append(FieldSlice, strings.Trim(fmt.Sprintf("%v.%v", table, f), "."))
		}
	}
	for index, table := range tables {
		slice := strings.Split(strings.TrimSpace(table), " ")
		if len(slice) == 1 {
			slice = append(slice, slice[0])
		}
		usedTables = append(usedTables, slice[1])
		if index > 0 {
			on, joinKV = joinOn(slice[1], usedTables, on)
			join = append(join, "left join "+table+" on "+joinKV)
		}
	}
	if len(orderBy) > 0 {
		StrOrderBy = " order by " + strings.Join(orderBy, ",")
	}
	if len(condition) > 0 {
		StrCondition = " where " + condition
	}
	if len(groupBy) > 0 {
		StrGroupBy = " group by " + strings.Join(groupBy, ",")
	}

	sql = fmt.Sprintf("select %v from %v %v %v %v limit %v offset %v", strings.Join(FieldSlice, ","), strings.Join(join, " "), StrCondition, StrGroupBy, StrOrderBy, listRows, (p-1)*listRows)
	return
}

//只供LeftJoinSqlBuild创建SQL语句使用
//@param                table               需要左联查询的表