mysql> set @v = null; Query OK, 0 rows affected (0.02 sec) mysql> select ifnull(@v,'wc'); +---+ | ifnull(@v,'wc') | +---+ | wc | +---+ 1 row in set (0.01 sec) 3、nullif(xx,yy) :如果xx=yy,则返回null,否则还是返回xx mysql> set @v = 'a'; Query OK, 0 row...
To show the similarity between NULLIF and CASE, the following queries evaluate whether the values in the MakeFlag and FinishedGoodsFlag columns are the same. The first query uses NULLIF. The second query uses the CASE expression. SQL Copy USE AdventureWorks2022; GO SELECT ProductID, MakeFlag,...
To show the similarity between NULLIF and CASE, the following queries evaluate whether the values in the MakeFlag and FinishedGoodsFlag columns are the same. The first query uses NULLIF. The second query uses the CASE expression.SQL نسخ ...
The function can be used only in the WHERE clause of a query. It takes as an argument a condition and returns TRUE if the condition is FALSE or UNKNOWN and FALSE if the condition is TRUE. 语法– ```sql LNNVL( condition(s) ) ``` 示例– ```sql SELECT COUNT(*) FROM employees ...
To show the similarity betweenNULLIFandCASE, the following queries evaluate whether the values in theMakeFlagandFinishedGoodsFlagcolumns are the same. The first query usesNULLIF. The second query uses theCASEexpression. SQL USEAdventureWorks2022; GOSELECTProductID, MakeFlag, FinishedGoodsFlag,NULLIF(Ma...
To show the similarity between NULLIF and CASE, the following queries evaluate whether the values in the MakeFlag and FinishedGoodsFlag columns are the same. The first query uses NULLIF. The second query uses the CASE expression.SQL Kopiraj ...
To show the similarity betweenNULLIFandCASE, the following queries evaluate whether the values in theMakeFlagandFinishedGoodsFlagcolumns are the same. The first query usesNULLIF. The second query uses theCASEexpression. SQL USEAdventureWorks2022; GOSELECTProductID, MakeFlag, FinishedGoodsFlag,NULLIF(Ma...
To show the similarity betweenNULLIFandCASE, the following queries evaluate whether the values in theMakeFlagandFinishedGoodsFlagcolumns are the same. The first query usesNULLIF. The second query uses theCASEexpression. SQLCopy USEAdventureWorks2022; GOSELECTProductID, MakeFlag, FinishedGoodsFlag,NULLIF...
A nice explanation of windowing functions on the three RDBMS can be found here:SQL Window Functions in SQL Server, Oracle and PostgreSQL. Oracle Let’s review the same example in Oracle with the following query: with invoice1 as (select invoiceid,customerid, total, ROW_NUMBER() over (partit...
Learn-SQL / PostgreSQL / How to Use nullif() in PostgreSQL Thenullif()function returns a null value, if a the value of the field/column defined by the first parameter equals that of the second. Otherwise, it will return the original value. Here's an example below: ...