124 lines
3.6 KiB
Markdown
124 lines
3.6 KiB
Markdown
# 5.4 PostgreSQL
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PostgreSQL is an object-relational database management system available for many platforms including Linux, FreeBSD, Solaris, Microsoft Windows and Mac OS X. It is released under an MIT-style license, and is thus free and open source software. It's larger than MySQL because it's designed for enterprise usage like Oracle. Postgresql is good choice for enterprise type projects.
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## PostgreSQL drivers
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There are many database drivers available for PostgreSQL. Here are three examples of them:
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- [https://github.com/bmizerany/pq](https://github.com/lib/pq) supports `database/sql`, written in pure Go.
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- [https://github.com/jbarham/gopgsqldriver](https://github.com/jbarham/gopgsqldriver) supports `database/sql`, written in pure Go.
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- [https://github.com/lxn/go-pgsql](https://github.com/lxn/go-pgsql) supports `database/sql`, written in pure Go.
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I'll use the first one in my following examples.
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## Samples
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We create the following SQL:
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CREATE TABLE userinfo
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(
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uid serial NOT NULL,
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username character varying(100) NOT NULL,
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departname character varying(500) NOT NULL,
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Created date,
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CONSTRAINT userinfo_pkey PRIMARY KEY (uid)
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)
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WITH (OIDS=FALSE);
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An example:
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package main
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import (
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"database/sql"
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"fmt"
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_ "github.com/lib/pq"
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"time"
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)
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const (
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DB_USER = "postgres"
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DB_PASSWORD = "postgres"
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DB_NAME = "test"
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)
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func main() {
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dbinfo := fmt.Sprintf("user=%s password=%s dbname=%s sslmode=disable",
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DB_USER, DB_PASSWORD, DB_NAME)
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db, err := sql.Open("postgres", dbinfo)
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checkErr(err)
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defer db.Close()
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fmt.Println("# Inserting values")
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var lastInsertId int
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err = db.QueryRow("INSERT INTO userinfo(username,departname,created) VALUES($1,$2,$3) returning uid;", "astaxie", "研发部门", "2012-12-09").Scan(&lastInsertId)
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checkErr(err)
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fmt.Println("last inserted id =", lastInsertId)
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fmt.Println("# Updating")
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stmt, err := db.Prepare("update userinfo set username=$1 where uid=$2")
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checkErr(err)
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res, err := stmt.Exec("astaxieupdate", lastInsertId)
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checkErr(err)
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affect, err := res.RowsAffected()
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checkErr(err)
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fmt.Println(affect, "rows changed")
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fmt.Println("# Querying")
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rows, err := db.Query("SELECT * FROM userinfo")
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checkErr(err)
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for rows.Next() {
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var uid int
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var username string
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var department string
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var created time.Time
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err = rows.Scan(&uid, &username, &department, &created)
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checkErr(err)
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fmt.Println("uid | username | department | created ")
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fmt.Printf("%3v | %8v | %6v | %6v\n", uid, username, department, created)
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}
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fmt.Println("# Deleting")
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stmt, err = db.Prepare("delete from userinfo where uid=$1")
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checkErr(err)
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res, err = stmt.Exec(lastInsertId)
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checkErr(err)
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affect, err = res.RowsAffected()
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checkErr(err)
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fmt.Println(affect, "rows changed")
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}
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func checkErr(err error) {
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if err != nil {
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panic(err)
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}
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}
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Note that PostgreSQL uses the `$1, $2` format instead of the `?` that MySQL uses, and it has a different DSN format in `sql.Open`.
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Another thing is that the Postgres driver does not support `sql.Result.LastInsertId()`.
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So instead of this,
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stmt, err := db.Prepare("INSERT INTO userinfo(username,departname,created) VALUES($1,$2,$3);")
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res, err := stmt.Exec("astaxie", "研发部门", "2012-12-09")
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fmt.Println(res.LastInsertId())
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use `db.QueryRow()` and `.Scan()` to get the value for the last inserted id.
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err = db.QueryRow("INSERT INTO TABLE_NAME values($1) returning uid;", VALUE1").Scan(&lastInsertId)
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fmt.Println(lastInsertId)
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## Links
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- [Directory](preface.md)
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- Previous section: [SQLite](05.3.md)
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- Next section: [Develop ORM based on beedb](05.5.md)
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