NewMySQL new db and retry connection when has error.

Open opens a database specified by its database driver name and a driver-specific data source name, usually consisting of at least a database name and connection information.

ErrNoMaster is returned by Master when call master multiple times.

ErrNoRows is returned by Scan when QueryRow doesn't return a row.

ErrStmtNil prepared stmt error.

ErrTxDone transaction done.

Config mysql config.

DB database.

Row row.

Rows rows.

Stmt prepared stmt.

Tx transaction.