dbconn.query golang sql example

Sure! Here's an example of using the query method in the database/sql package in Go:

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/go-sql-driver/mysql"
    "log"
)

func main() {
    // Open a connection to the database
    db, err := sql.Open("mysql", "username:password@tcp(localhost:3306)/database")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    // Execute a query
    rows, err := db.Query("SELECT id, name, age FROM users")
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()

    // Iterate over the result set
    for rows.Next() {
        var id int
        var name string
        var age int
        if err := rows.Scan(&id, &name, &age); err != nil {
            log.Fatal(err)
        }
        fmt.Println("ID:", id, "Name:", name, "Age:", age)
    }

    // Check for any errors during iteration
    if err := rows.Err(); err != nil {
        log.Fatal(err)
    }
}

In this example, we first open a connection to the database using the sql.Open function, specifying the driver and connection string. Then, we use the db.Query method to execute the SQL query and obtain a *sql.Rows result set.

We iterate over the result set using the rows.Next method and retrieve the values using the rows.Scan method. Finally, we print the values and check for any errors during iteration using rows.Err.

Note that you need to import the appropriate database driver package, in this case github.com/go-sql-driver/mysql, and replace the connection string with your own MySQL database details.

To execute a query with parameters in Go using the database/sql package, you can use the Query method along with placeholders for the parameters. Here's an example:

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/go-sql-driver/mysql"
    "log"
)

func main() {
    // Open a connection to the database
    db, err := sql.Open("mysql", "username:password@tcp(localhost:3306)/database")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    // Prepare the SQL statement with placeholders
    stmt, err := db.Prepare("SELECT id, name, age FROM users WHERE age > ?")
    if err != nil {
        log.Fatal(err)
    }
    defer stmt.Close()

    // Execute the query with the parameter value
    rows, err := stmt.Query(18)
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()

    // Iterate over the result set
    for rows.Next() {
        var id int
        var name string
        var age int
        if err := rows.Scan(&id, &name, &age); err != nil {
            log.Fatal(err)
        }
        fmt.Println("ID:", id, "Name:", name, "Age:", age)
    }

    // Check for any errors during iteration
    if err := rows.Err(); err != nil {
        log.Fatal(err)
    }
}

In this example, we first open a connection to the database using sql.Open and then prepare the SQL statement using db.Prepare, specifying the SQL query with a placeholder ? for the parameter.

We then execute the query using stmt.Query, passing the parameter value (in this case, 18). The result set is iterated over in the same way as before, using rows.Next and rows.Scan.

Note that you need to import the appropriate database driver package, in this case github.com/go-sql-driver/mysql, and replace the connection string with your own MySQL database details.

If you want to use positional parameters in your SQL query instead of placeholders, you can modify the example as follows:

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/go-sql-driver/mysql"
    "log"
)

func main() {
    // Open a connection to the database
    db, err := sql.Open("mysql", "username:password@tcp(localhost:3306)/database")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    // Prepare the SQL statement with positional parameter
    stmt, err := db.Prepare("SELECT id, name, age FROM users WHERE age > ?")
    if err != nil {
        log.Fatal(err)
    }
    defer stmt.Close()

    // Execute the query with the positional parameter value
    rows, err := stmt.Query(18)
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()

    // Iterate over the result set
    for rows.Next() {
        var id int
        var name string
        var age int
        if err := rows.Scan(&id, &name, &age); err != nil {
            log.Fatal(err)
        }
        fmt.Println("ID:", id, "Name:", name, "Age:", age)
    }

    // Check for any errors during iteration
    if err := rows.Err(); err != nil {
        log.Fatal(err)
    }
}

In this modified example, we use the ? placeholder in the SQL query. When preparing the statement, we don't need to specify the positional parameter explicitly. Instead, we directly pass the parameter value (in this case, 18) to stmt.Query.

Note that the behavior of placeholders and positional parameters may vary depending on the database driver you are using. The example provided assumes the MySQL driver, but other drivers may use different syntax or conventions for parameters.