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...
In this example, if the deptno column has a 10 in it, the SQL query will return the value accounting rather than the number 10. If the deptno is not 10, 20, 30, or 40, then the CASE statement will fall through to the ELSE clause, which will return unassigned. Note that with a s...
If you want to find all the exam results with A or B grades, you can place theselectabove in a subquery. Then filter it in the outer query. Or you can slap thecaseexpression directly in thewhereclause, like so: Using columns incaseexpressions like this limits the optimizer’s ability...
Oracle的CASE WHEN语法是一种在数据库查询中使用的条件语句,它提供了一种在SELECT语句中根据条件对结果进行转换或筛选的方法。在本文中,我们将详细介绍Oracle的CASE WHEN语法,并提供一些实际的示例。 CASE WHEN语句的基本语法结构如下: CASE WHEN condition1 THEN result1 ...
select * from dept minus select * from dept where rownum < (select count (*) from 表名); -- 42、在 Oracle 中做行数据乘法 with tbl as (select -2 num from dual union select -3 num from dual union select -4 num from dual), sign_val as (select case mod (count (*), 2) when...
1、使用sys或其他用户修改表名 代码语言:javascript 代码运行次数:0 SQL>show user;USERis"SYS"SQL>alter table user1.tb1 rename to user1tb2ERRORat line1:ORA-14047:ALTERTABLE|INDEXRENAMEmay not be combinedwithother operations #使用非属主用户修改表名时修改后的表名不需要加属主 ...
Occurs when the query coordinator is waiting for a response from a parallel slave. This is normally considered an idle event, but can cause excessive CPU in some cases. Waiting Process: QC 协调器正在等待一个 从slaves 进程对控制信息的响应(确认通知)或者期望从slave进程集中获取数据。这个等待事件意...
ourSQLquery,definingtheaggregations,whichcanthenbenamedinthemain queryasiftheywere"real"tables: WITH subquery_name AS (theaggregationSQLstatement) SELECT (querynamingsubquery_name); ...
如下Q14是TPC-H query2的简版。外部查询比子查询多了PARTS表和一个PARTS表的过滤谓词。Q14中子查询与外层查询的关联字段是P.p_partkey = ps_partkey,因此,Q15中的partition key为ps_partkey。Uncorrelated Subsumed Subquery 如下Q 17是TPC-H query15的简版。Q17中,有一个With子句,含有非相关agg子查询,子...
SQL> alter system set sec_case_sensitive_logon = false; System altered. SQL> conn scott/TIGER Connected. 在将现有 Oracle 10g数据库升级到 11g时,可将口令迁移到新标准。可以通过查询 DBA_USERS 视图来检查口令状态,尤其是新的 PASSWORD_VERSIONS 列。