MySQL/SQLite: support returning LastInsertId

[housingdreams]

:exec only checks the error
:execresult returns the full sql.Result
:execrows returns the sql.Result.RowsAffected() (int64, error)

We just need one more return type to support the full interface:

:execlastinsertid would just be a matter of calling .LastInsertId() rather than .RowsAffected() on the sql.Result.

This will avoid sql.Result database information leaking across the boundary of the pkg.Querier interface. It's not good for the service code to be handling DB specific method calls. This is a MySQL/SQLite issue as Postgres uses RETURNING so you can use :one instead.

Solution: duplicate the template code used for :execrows

[lpintes]

Recent versions of MariaDB supports returning clause in insert statement. So perhaps fixing parser could be sufficient.

[housingdreams]

Unfortunately, there are a lot of companies still running older MySQL installs. In addition, using sqlc with products like TiDB or https://vitess.io/ would also require this.

[Jille]

(I requested this before in #1200. I agree it would be nicer to have a :execinsertid)

[kyleconroy]

This has been added as :execlastid and will ship in 1.14.0