support bulk insert

[mackee]

What's this?

Support the insert of multiple rows for MySQL and SQLite (3.7.11 or later).

See also: https://dev.mysql.com/doc/refman/8.0/en/insert.html , https://www.sqlite.org/lang_insert.html

Usage

You can call BulkInsert() after the New**SQL(). This returns a **BulkInsertSQL object. It can have multiple **InsertSQL object.

Example:

bq := NewFooSQL().BulkInsert()
for i := 0; i < 3; i++ {
    q := NewFooSQL().Insert().ValueBar(i)
    bq.Append(q)
}

// INSERT INTO `foo` (`bar`) VALUES (?),(?),(?); [0 1 2]
if _, err := bq.ExecContext(ctx, db); err != nil {
    return err
}

Also, **BulkInsert can call OnDuplicateKeyUpdate(). If you need append ON DULICATE KEY UPDATE ~ to the suffix, call this.

Example:

bq := NewFooSQL().BulkInsert()
bq.Append(...)

// INSERT INTO `foo` (`bar`) VALUES (?),(?) ON DUPLICATE KEY UPDATE `bar` = VALUES(`bar`);
_, err := bq.OnDuplicateKeyUpdate().
    SameValueOnUpdateFoo()