mysql - sql COMPOSITE KEY帮助

使用sql，我需要将Lineno和orderline组合成一个组合键，到目前为止，我有

CREATE TABLE ORDERLINE (
   ORDERNO INTEGER NOT NULL,
   LINENO VARCHAR(4) NOT NULL,
   NUMBERORDERED NUMERIC DEFAULT '1',
   QUOTEDPRICE NUMERIC DEFAULT '0.00',
   CONSTRAINT ORDERLINE_ORDERNO_PK PRIMARY KEY (ORDERNO),
   CONSTRAINT ORDERLINE_ORDERNO_CC CHECK (ORDERNO BETWEEN 10000 AND 99999),
   CONSTRAINT ORDERLINE_NUMBERORDERED CHECK (NUMBERORDERED BETWEEN 1 AND 100)
);

最佳答案

CREATE TABLE ORDERLINE (
    ORDERNO INTEGER NOT NULL,
    LINENO VARCHAR(4) NOT NULL,
    NUMBERORDERED NUMERIC DEFAULT '1',
    QUOTEDPRICE NUMERIC DEFAULT '0.00',
    CONSTRAINT ORDERLINE_ORDERNO_PK PRIMARY KEY(ORDERNO, LINENO), -- note alteration on this line
    CONSTRAINT ORDERLINE_ORDERNO_CC CHECK (ORDERNO BETWEEN 10000 AND 99999),
    CONSTRAINT ORDERLINE_NUMBERORDERED CHECK (NUMBERORDERED BETWEEN 1 AND 100)
);

你离得很近。注意上面添加的列名。
确定哪个字段更可能是任何查询中的前导列，并将其放在第一位。例如，如果您经常按OrderNO访问，那么LineNo将是最好的顺序，如果您按LineNo访问，OrderNO将跟随该顺序。

关于mysql - sql COMPOSITE KEY帮助，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/6172816/