Nomor Dokumen

DROP TABLE IF EXISTS no_dokumen;
CREATE TABLE IF NOT EXISTS no_dokumen(
    nomor INT AUTO_INCREMENT,
    dokumen CHAR(1),
    PRIMARY KEY(dokumen,nomor)
) ENGINE=MyISAM;

INSERT INTO no_dokumen(dokumen)
VALUES('A'),('A'),('B'),('C'),('A'),('B'),('C'),('B'),('B');

SELECT * FROM no_dokumen;
+-------+---------+
| nomor | dokumen |
+-------+---------+
|     1 | A       |
|     2 | A       |
|     3 | A       |
|     1 | B       |
|     2 | B       |
|     3 | B       |
|     4 | B       |
|     1 | C       |
|     2 | C       |
+-------+---------+

INSERT INTO no_dokumen(dokumen)
VALUES('A'),('B'),('A'),('C');

+-------+---------+
| nomor | dokumen |
+-------+---------+
|     1 | A       |
|     2 | A       |
|     3 | A       |
|     4 | A       |
|     5 | A       |
|     1 | B       |
|     2 | B       |
|     3 | B       |
|     4 | B       |
|     5 | B       |
|     1 | C       |
|     2 | C       |
|     3 | C       |
+-------+---------+