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This article shows you the details of the SQL sentence Count, which is concise and easy to understand, which will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

The count statement supports *, column names, constants, variables, and can be modified with the distinct keyword, and count (column names) does not accumulate null records. Here are some random examples to demonstrate the rules of count:

For example, to do statistics on the following table, all the columns are represented by the sql_variant type.

The code is as follows:

If (object_id ('sql_variant') > 0) drop table t_test go create table t_test (a sql_variant, b sql_variant, c sql_variant) insert into t_test select 1, 1,'a 'insert into t_test select 1, getdate (), null insert into t_test select 'a', null, 1 insert into t_test select 3, null, null insert into t_test select null, null, null go select * from t_test go select count (*)-Total

Count (nullif (1,1))-always returns 0

Count (a)-a quantity

Count (b)-- b quantity

Count (distinct a)-a does not repeat the quantity

Count (isnull (b, c))-b or c is not the number of null

Count (Coalesce (a, b, c))-an or b or c is not the number of null

Count (nullif (a, b))-an is not equal to the number of b

Count (nullif (isnumeric (cast (an as varchar (38)), 0))-an is the number of numbers from t_test

What are the details of the SQL statement Count? have you learned any knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

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