DECODE is considered the most powerful function in Oracle. Oracle 8i release introduced the CASE expression. The CASE expression can do all that DECODE does plus lot of other things including IF-THEN analysis, use of any comparison operator and checking multiple conditions, all in a SQL query i...
是指在Oracle数据库中,使用SELECT语句查询数据时,可以将一个SELECT语句作为子查询嵌套在另一个SELECT语句的CASE语句中。 具体来说,CASE语句是一种条件表达式,用于根据条件返...
1、sql中,这两个函数我们仅能使用case,代码及结果如下: select name, case Subject when '语文' then 1 when '数学' then 2 when '英语' then 3 --else 3 end as '科目代码' from Results 同样的,我们可以用case实现行转列,代码及结果如下: select Name, sum(case when Subject='语文' then Result...
SELECT column1, column2, CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ELSE result3 END AS new_column1, CASE WHEN condition4 THEN result4 WHEN condition5 THEN result5 ELSE result6 END AS new_column2 FROM table_name; 在这个示例中,我们根据不同的条件(condition1、condition2...
SQL>show userUSER为"HR"SQL>SELECTfirst_name,last_name,department_id,2CASEdepartment_id3WHEN10THEN'Accounting'4WHEN20THEN'Sales'5WHEN30THEN'Finance'6ELSE'Other'7ENDdepartment_name8FROMemployees where rownum<2;FIRST_NAMELAST_NAMEDEPARTMENT_IDDEPARTMENT_NAME---Steven King90OtherSQL> ※测试使用的Orac...
It would be better to list and check it once, like a simple case expression. FromOracle Database 23aiyou can get the “best of both” with extended case controls. These enable you to: List and evaluate the selector once Compare it using all SQL conditions ...
selectcasewhen (select count(*) from table2 where id=table1.id)>0 then'table2 and table1 is related'when (select count(*) from table3 where id=table1.id)>0 then'table3 and table1 is related'else'no table related with table1'endfrom table1像这样的...
CASE表达式可以再SQL中实现if-then-else型的逻辑,9i及以上版本支持CASE表达式。 1. 使用简单CASE表达式 语法如下: CASE search_expression WHENexpression1 THEN result1 … ELSEdefault_result END store@PDB1> select product_id,product_type_id,caseproduct_type_id ...
哦,好吧!是不是感觉很麻烦,下面我用with语句来写SQL语句: with e as ( select deptno dno,max(sal) max_sal from emp group by deptno) select m.empno,m.ename,m.sal,m.hiredate,d.deptno,d.dname from e,emp m,dept d where e.dno=m.deptno and m.deptno=d.deptno and e.max_sal=m.sal ...
select * from Employee where age>22 // 更新数据 UPDATE Employee SET name = 'Felex' WHERE age = 25 // 删除数据 delete from Employee where age<21 Select语句基本结构 Select [Distinct] {column1,column2,…} From tablename Where {conditions} ...