在TREX上找不到"Null值"中文 - 英语方向
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Null值)
但是,在任何SQL聚合函数中都不会计算Null值。
However, Null values are not evaluated in any SQL aggregate function.NULL值也没有效果,但是递增NULL的结果是1。
Decrementing NULL values has no effect too, but incrementing them results in 1.
It forms a separate type of its own which contains only the null value.
In the first record of an internal table, the function returns NULL.
A null value("" or NULL) would create an error.递减NULL值也没有效果,但是递增NULL的结果是1。
Decrementing NULL values has no effect too, but incrementing them results in 1.
The Nz function is useful for expressions that may include Null values.现在,由开发人员决定如果处理这种潜在的null值。
It's now up to me to decide how I want to handle this potentially null value.您不能使用比较操作符测试NULL值,例如=、<或<>。
It is not possible to test for NULL values with comparison operators, such as=,<, or<>我们如何才能选择"Address"列中有NULL值的记录??
How do we select only the records with NULL values in the"Address" column?
In the first record of an internal table, the function will return NULL.我们如何仅仅选取在"Address"列中带有NULL值的记录呢??
How do we select only the records with NULL values in the"Address" column?以这种方式调用COUNT()仅返回不包含NULL值的行。
Invoking COUNT() in that way only returns rows which are not comprised of NULL values.
The special NULL value represents a variable with no value..要区分输入数据中存在的NULL值与分组运算符插入的NULL值,请使用GROUPING函数。
To distinguish between NULL values present in the input data and NULL values inserted by the grouping operator, use the GROUPING function.我们如何仅仅选取在"Address"列中不带有NULL值的记录呢??
How do we select only the records with no NULL values in the"Address" column?我们如何选取在"Address"列中不带有NULL值的记录呢??
How do we select only the records with no NULL values in the"Address" column?因此,以下SELECT查询将获取description列包含非NULL值的行数.
Hence, the following SELECT query would fetch the number of rows where the description column contained a non-NULL value.
NOT NULL Constraint: Ensures that a column cannot have NULL value.Zero静态公共字段,以便获得用于比较或赋值的null值。
Zero static public field on the IntPtr type to get the null value for comparing or assigning.
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