What is the usage of case when in oracle

In Oracle, "case when" is used to determine the multi-state situation of a field. The syntax is "case column name when condition value 1 then option 1 when condition value 2 then option 2...else default value end ".

The operating environment of this tutorial: Windows 10 system, Oracle 11g version, Dell G3 computer.

What is the usage of case when in oracle

oracle case when usage

Case has two formats. Simple Case function and Case search function.

Usage of Case when in Oracle:

(a) Starts with case and ends with end;

(b) When is followed by condition, then displays the result ;

(c) else is the default case, similar to the switch case in high-level language programs. The default can be omitted;

(d) end is followed by an alias;

Case has two kinds of expressions:

(A) Simple case expressions use expressions to determine the return value;

(B) Search case expressions and use conditions to determine the return value Value;

First format: Simple Case function:

Format description

　　　　case 列名
　　　　when 条件值1 then 选项1
　　　　when 条件值2 then 选项2.......
　　　　else 默认值 end

eg:

　　　　select 
　　　　case 　　job_level
　　　　when '1' then '1111'
　　　　when　 '2' then '1111'
　　　　when　 '3' then '1111'
　　　　else 'eee' end
　　　　from dbo.employee

Second format:Case search function

Format description

　　　　case
　　　　when 列名= 条件值1 then 选项1
　　　　when 列名=条件值2 then 选项2.......
　　　　else 默认值 end

eg:

　　　　update employee
　　　　set e_wage =
　　　　case
　　　　when job_level = '1' then e_wage*1.97
　　　　when job_level = '2' then e_wage*1.07
　　　　when job_level = '3' then e_wage*1.06
　　　　else e_wage*1.05
　　　　end

Recommended tutorial: "Oracle Video Tutorial"

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