How to execute an IN lookup in SQL using Golang?

问题:

What does Go want for the second param in this SQL query. I am trying to use the IN lookup in postgres.

stmt, err := db.Prepare("SELECT * FROM awesome_table WHERE id= $1 AND other_field IN $2")
rows, err := stmt.Query(10, ???)

What I really want:

SELECT * FROM awesome_table WHERE id=10 AND other_field IN (this, that);

回答1:

Query just takes varargs to replace the params in your sql so, in your example, you would just do

rows, err := stmt.Query(10)

say, this and that of your second example were dynamic, then you'd do

stmt, err := db.Prepare("SELECT * FROM awesome_table WHERE id=$1 AND other_field IN ($2, $3)")
rows, err := stmt.Query(10,"this","that")

If you have variable args for the "IN" part, you can do (play)

package main

import "fmt"
import "strings"

func main() {
    stuff := []interface{}{"this", "that", "otherthing"}
    sql := "select * from foo where id=? and name in (?" + strings.Repeat(",?", len(stuff)-1) + ")"
    fmt.Println("SQL:", sql)
    args := []interface{}{10}
    args = append(args, stuff...)
    fakeExec(args...)
    // This also works, but I think it's harder for folks to read
    //fakeExec(append([]interface{}{10},stuff...)...)
}

func fakeExec(args ...interface{}) {
    fmt.Println("Got:", args)
}

回答2:

It looks like you may be using the pq driver. pq recently added Postgres-specific Array support via pq.Array (see pull request 466). You can get what you want via:

stmt, err := db.Prepare("SELECT * FROM awesome_table WHERE id= $1 AND other_field = ANY($2)")
rows, err := stmt.Query(10, pq.Array([]string{'this','that'})

I think this generates the SQL:

SELECT * FROM awesome_table WHERE id=10 AND other_field = ANY('{"this", "that"}');

Note this utilizes prepared statements, so the inputs should be sanitized.

回答3:

Incase anyone like me was trying to use an array with a query, here is an easy solution.

get https://github.com/jmoiron/sqlx

ids := []int{1, 2, 3}
q,args,err := sqlx.In("SELECT id,username FROM users WHERE id IN(?);", ids) //creates the query string and arguments
//you should check for errors of course
q = sqlx.Rebind(sqlx.DOLLAR,q) //only if postgres
rows, err := db.Query(q,args...) //use normal POSTGRES/ANY SQL driver important to include the '...' after the Slice(array)

回答4:

With PostgreSQL, at least, you have the option of passing the entire array as a string, using a single placeholder:

db.Query("select 1 = any($1::integer[])", "{1,2,3}")

That way, you can use a single query string, and all the string concatenation is confined to the parameter. And if the parameter is malformed, you don't get an SQL injection; you just get something like: ERROR: invalid input syntax for integer: "xyz"

https://groups.google.com/d/msg/golang-nuts/vHbg09g7s2I/RKU7XsO25SIJ

回答5:

You can also use this direct conversion.

awesome_id_list := []int{3,5,8}

var str string
for _, value := range awesome_id_list {
        str += strconv.Itoa(value) + ","
}

query := "SELECT * FROM awesome_table WHERE id IN (" + str[:len(str)-1] + ")"

WARNING
This is method is vulnerable to SQL Injection. Use this method only if awesome_id_list is server generated.

回答6:

Rather pedestrian and only to be used if server generated. Where UserIDs is a slice (list) of strings:

sqlc := `select count(*) from test.Logins where UserID 
                in ("` + strings.Join(UserIDs,`","`) + `")`
errc := db.QueryRow(sqlc).Scan(&Logins)