Define a primary key to enforce uniqueness for values entered in specified columns that do not allow nulls.

定义主键以对不允许空值的指定列中输入的值强制唯一性。

youdao

For each of the columns, be sure to select the right data type and to uncheck the Allow Nulls options.

对每个列，要确保选择了正确的数据类型，并取消“允许为空”复选框。

youdao

For each of the columns, be sure to select the right data type and to uncheck the Allow Nulls options.

对每个列，要确保选择了正确的数据类型，并取消“允许为空”复选框。

youdao