How to connect a Go application to a database
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14
test_connect/go.mod
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14
test_connect/go.mod
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module test_connect
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go 1.22.5
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require github.com/jackc/pgx/v5 v5.6.0
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require (
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github.com/jackc/pgpassfile v1.0.0 // indirect
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github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
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github.com/jackc/puddle/v2 v2.2.1 // indirect
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golang.org/x/crypto v0.25.0 // indirect
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golang.org/x/sync v0.7.0 // indirect
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golang.org/x/text v0.16.0 // indirect
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)
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28
test_connect/go.sum
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test_connect/go.sum
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github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
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github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
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github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
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github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
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github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
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github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a h1:bbPeKD0xmW/Y25WS6cokEszi5g+S0QxI/d45PkRi7Nk=
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github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
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github.com/jackc/pgx/v5 v5.6.0 h1:SWJzexBzPL5jb0GEsrPMLIsi/3jOo7RHlzTjcAeDrPY=
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github.com/jackc/pgx/v5 v5.6.0/go.mod h1:DNZ/vlrUnhWCoFGxHAG8U2ljioxukquj7utPDgtQdTw=
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github.com/jackc/puddle/v2 v2.2.1 h1:RhxXJtFG022u4ibrCSMSiu5aOq1i77R3OHKNJj77OAk=
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github.com/jackc/puddle/v2 v2.2.1/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
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github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
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github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
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github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
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github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
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github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
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github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
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github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
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golang.org/x/crypto v0.25.0 h1:ypSNr+bnYL2YhwoMt2zPxHFmbAN1KZs/njMG3hxUp30=
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golang.org/x/crypto v0.25.0/go.mod h1:T+wALwcMOSE0kXgUAnPAHqTLW+XHgcELELW8VaDgm/M=
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golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
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golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
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golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
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golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=
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gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
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gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
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gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
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gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
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123
test_connect/main.go
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test_connect/main.go
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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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"log"
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"os"
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_ "github.com/jackc/pgx/v5/stdlib"
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)
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func main() {
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// connect to a database
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conn, err := sql.Open("pgx", fmt.Sprintf("host=localhost port=5432 dbname=test_connect user=%s password=%s", os.Getenv("PGUSER"), os.Getenv("PGPWD")))
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if err != nil {
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log.Fatalf("Unable to connect to the database: %v\n", err)
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}
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defer conn.Close()
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log.Println("Connected to database!")
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// test my connection
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err = conn.Ping()
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if err != nil {
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log.Fatal("Cannot ping database!")
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}
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log.Println("Pinged database!")
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// get rows from table
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err = getAllRows(conn)
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if err != nil {
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log.Fatal(err)
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}
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// insert a row
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query := `insert into users (first_name, last_name) values ($1, $2)`
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_, err = conn.Exec(query, "Jack", "Brown")
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Inserted a row!")
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// get rows from table again
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err = getAllRows(conn)
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if err != nil {
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log.Fatal(err)
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}
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// update a row
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stmt := `update users set first_name = $1 where first_name = $2`
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_, err = conn.Exec(stmt, "Jackie", "Jack")
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Updated one or more rows")
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// get rows from table again
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err = getAllRows(conn)
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if err != nil {
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log.Fatal(err)
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}
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// get one row by id
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var firstName, lastName string
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var id int
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query = `select id, first_name, last_name from users where id = $1`
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row := conn.QueryRow(query, 1)
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err = row.Scan(&id, &firstName, &lastName)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Query row returns", id, firstName, lastName)
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// delete a row
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query = `delete from users where id = $1`
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_, err = conn.Exec(query, 3)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Delete a row")
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// get rows again
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err = getAllRows(conn)
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if err != nil {
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log.Fatal(err)
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}
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}
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func getAllRows(conn *sql.DB) error {
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rows, err := conn.Query("select id, first_name, last_name from users")
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if err != nil {
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log.Println(err)
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return err
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}
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defer rows.Close() // IMPORTANT!!
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var firstName, lastName string
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var id int
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for rows.Next() {
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err := rows.Scan(&id, &firstName, &lastName)
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if err != nil {
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log.Println(err)
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return err
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}
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fmt.Println("Record is", id, firstName, lastName)
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}
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if err = rows.Err(); err != nil {
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log.Fatalf("Error scanning rows: %v", err)
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}
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fmt.Println("----------------------------")
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return nil
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}
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