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...
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 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 ...
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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,...
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...
本文选自《Oracle程序员面试笔试宝典》,作者:李华荣。 About Me:小麦苗 ● 本文作者:小麦苗,只专注于数据库的技术,更注重技术的运用 ● 作者博客地址:http://blog.itpub.net/26736162/abstract/1/ ● 本系列题目来源于作者的学习笔记,部分整理自网络,若有侵权或不当之处还请谅解 ...
SQL - Temporary Tables SQL - Alter Tables SQL - Drop Table SQL - Delete Table SQL - Constraints SQL Queries SQL - Insert Query SQL - Select Query SQL - Select Into SQL - Insert Into Select SQL - Update Query SQL - Delete Query SQL - Sorting Results SQL Views SQL - Create Views SQL...
DECODE函数的作用:它可以将输入数值与函数中的参数列表相比较,根据输入值返回一个对应值。函数的参数列表是由若干数值及其对应结果值组成的若干序偶形式。当然,如果未能与任何一个实参序偶匹配成功,则函数也有默认的返回值。 区别于SQL的其它函数,DECODE函数还能识别和操作空值。
【SAP HANA系列】SAP HANA SQL IFNULL和NULLIF用法与区别 正文部分 SAP HANA SQL中有IFNULL,还有NULLIF 两者的用法和区别简单说一下 IFNULL是返回第一个不为NULL的数据 用法如下: NULLIF是比较前后两个参数是否相等 如果相等,返回NULL 如果不等,返回第一个参数 用法如下: 如果两个参数相等,如下...