wherein

Documentation

Overview

Package wherein expands SQL statements that have placeholders that can accept slices of arguments. This is most commonly useful for SQL statements that might look something like

SELECT * FROM table_name WHERE column_name IN (?)

If the argument associated with the placeholder is a slice containing (say) three values, then the SQL would be expanded to

SELECT * FROM table_name where column_name in (?,?,?)

See the example for more details.

Index

• func Expand(query string, args []interface{}) (newQuery string, newArgs []interface{}, err error)

Examples

• Expand

Functions

func Expand

func Expand(query string, args []interface{}) (newQuery string, newArgs []interface{}, err error)

Expand takes an SQL query and associated arguments and expands out any arguments that are a slice of values. Returns the new, expanded SQL query with arguments that have been flattened into a slice of scalar argument values.

If args contains only scalar values, then query and args are returned unchanged.

Example

// Using MySQL/SQLite style positional placeholders
{
	sql := "SELECT * FROM table_name WHERE column1 IN (?) and column2 = ?"
	args := []interface{}{
		[]int{101, 102, 103},
		"abc",
	}
	newSQL, newArgs, err := Expand(sql, args)
	if err != nil {
		fmt.Print(err)
		return
	}
	fmt.Printf("sql = %s\nargs = %v\n\n", newSQL, newArgs)
}

// Using PostgreSQL style numbered placeholders
{
	sql := "SELECT * FROM table_name WHERE column1 IN ($1) and column2 = $2"
	args := []interface{}{
		[]int{101, 102, 103},
		"abc",
	}
	newSQL, newArgs, err := Expand(sql, args)
	if err != nil {
		fmt.Print(err)
		return
	}
	fmt.Printf("sql = %s\nargs = %v\n\n", newSQL, newArgs)
}

// Using MySQL/SQLite style numbered placeholders
{
	sql := "SELECT * FROM table_name WHERE column1 IN (?2) and column2 IN (?1)"
	args := []interface{}{
		[]int{101, 102, 103},
		[]string{"abc", "def", "ghi"},
	}
	newSQL, newArgs, err := Expand(sql, args)
	if err != nil {
		fmt.Print(err)
		return
	}
	fmt.Printf("sql = %s\nargs = %v\n\n", newSQL, newArgs)
}

Output:

sql = SELECT * FROM table_name WHERE column1 IN (?,?,?) and column2 = ?
args = [101 102 103 abc]

sql = SELECT * FROM table_name WHERE column1 IN ($1,$2,$3) and column2 = $4
args = [101 102 103 abc]

sql = SELECT * FROM table_name WHERE column1 IN (?4,?5,?6) and column2 IN (?1,?2,?3)
args = [101 102 103 abc def ghi]