MYSQL 如何使一个字段「留空」或「非重」

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对某个字段的要求是，要么空，要么有不能重复的数值，请问 MYSQL 如何实现？

1 replies • 2015-09-16 18:11:28 +08:00

echo1937

Sep 16, 2015

mysql> ALTER TABLE tbl_name ADD [COLUMN] (col_name data_type DEFAULT NULL UNIQUE );