No, take the case to replace it.
For example, the following statement shows the Chinese month
Copy Code code as follows:
Select GETDATE () as date, Case month (GETDATE ())
When one then ' 11 '
When then ' 12 '
else substring (' 1,234,567,890 ', Month (getdate ()), 1)
End+ ' Month ' as month
The case may be one of the most misused keywords in SQL. Although you may have used this keyword before to create a field, it has more usage. For example, you can use the case in the WHERE clause.
First let's take a look at the syntax of the case. In a general SELECT, the syntax is as follows:
Copy Code code as follows:
SELECT <myColumnSpec> =
Case
When <A> THEN <somethingA>
When <B> THEN <somethingB>
ELSE <somethingE>
End
In the above code, you need to replace the contents of the angle brackets with specific parameters. The following is a simple example:
Copy Code code as follows:
Use pubs
Go
SELECT
Title,
' Price Range ' =
Case
When Price is NULL THEN ' unpriced '
When Price < THEN ' Bargain '
When Price BETWEEN and THEN ' Average '
ELSE ' Gift to impress relatives '
End
From titles
ORDER BY Price
Go
This is a typical use of case, but there are more things you can do with it. For example, the following case in the GROUP by clause:
Copy Code code as follows:
SELECT ' number of Titles ', Count (*)
From titles
GROUP by
Case
When Price is NULL THEN ' unpriced '
When Price < THEN ' Bargain '
When Price BETWEEN and THEN ' Average '
ELSE ' Gift to impress relatives '
End
Go
You can even combine these options and add an ORDER BY clause as follows:
Copy Code code as follows:
Use pubs
Go
SELECT
Case
When Price is NULL THEN ' unpriced '
When Price < THEN ' Bargain '
When Price BETWEEN and THEN ' Average '
ELSE ' Gift to impress relatives '
End as Range,
Title
From titles
GROUP by
Case
When Price is NULL THEN ' unpriced '
When Price < THEN ' Bargain '
When Price BETWEEN and THEN ' Average '
ELSE ' Gift to impress relatives '
End,
Title
ORDER BY
Case
When Price is NULL THEN ' unpriced '
When Price < THEN ' Bargain '
When Price BETWEEN and THEN ' Average '
ELSE ' Gift to impress relatives '
End,
Title
Go
Note that in order to use case in the group by block, the query statement needs to repeat the case block in the SELECT block in the group by block.
In addition to selecting custom fields, cases are useful in many cases. In a further step, you can also get a set of sorted results that you previously thought would be impossible.
