OR ） CASE WHEN sex = ‘1’ THEN ‘男’ WHEN sex = ‘2’ THEN ‘女’ ELSE ‘其他’ END...
1 CASE WHEN Case when语句能在SQL语句中织入判断逻辑,类似于Java中的if else语句。...END 解释一下,语句中的condition是条件判断,如果该判断结果为true,那么CASE语句将返回result,否则返回result2,如果没有ELSE,则返回null。...因此,我们希望在SQL中做一些处理,如果查询结果是null,就转换为特定的值,...
SELECTcolumn1, column2, ...CASEWHENcondition1THENresult1WHENcondition2THENresult2-- Add more WHEN conditions and results as neededENDASalias_nameFROMtable_name; We can add as manyWHEN ... THENconditions as required in theCASEstatement. For example, -- multiple CASE conditions in SQLSELECTcusto...
-- Deriving multiple logical records from each physical record. -- -- Using a WHEN clause. -- -- Loading the same field (empno) into multiple tables. -- -- TO RUN THIS CASE STUDY: -- 1. Before executing this control file, log in to SQL*Plus as -- scott/tiger. Enter @ulcase5 ...
The output fromEXPLAINshowsALLin thetypecolumn when MySQL uses afull table scanto resolve a query. 慢SQL 分析与优化 https://mp.weixin.qq.com/s/CaSVhAJgycjjbCxAkII2ZA 从系统设计角度看,一个系统从设计搭建到数据逐步增长,SQL 执行效率可能会出现劣化,为继续支撑业务发展,我们需要对慢 SQL 进行分析和...
报错:Update row with Key (id)=(xxxx) multiple times或者duplicate key value violates unique constraint 问题原因:违反唯一性约束,执行UPDATE、INSERT ON CONFLICT或INSERT操作时,主键存在重复数据。 解决方法: 若INSERT语法报错:可以改为INSERT INTO xx ON CONFLICT的语法,实现主键去重,详情请参见INSERT ON CONFLIC...
Multiple Lateral View可以实现类似笛卡尔乘积。 Outer关键字可以把不输出的UDTF的空结果,输出成NULL,防止丢失数据。 行转列 相关参数说明: CONCAT(string A/col, string B/col…):返回输入字符串连接后的结果,支持任意个输入字符串; CONCAT_WS(separator, str1, str2,...):它是一个特殊形式的 ...
Evaluates a list of conditions and returns one of multiple possible result expressions. TheCASEexpression has two formats: The simpleCASEexpression compares an expression to a set of simple expressions to determine the result. The searchedCASEexpression evaluates a set of Boolean expressions to determin...
Evaluates a list of conditions and returns one of multiple possible result expressions. TheCASEexpression has two formats: The simpleCASEexpression compares an expression to a set of simple expressions to determine the result. The searchedCASEexpression evaluates a set of Boolean expressions to determin...
MULTIPLE_LOAD_PATH, MULTIPLE_QUERY_RESULT_CLAUSES_WITH_PIPE_OPERATORS, NAMESPACE_ALREADY_EXISTS, NAMESPACE_NOT_EMPTY, NAMESPACE_NOT_FOUND, NON_PARTITION_COLUMN, NOTEBOOK_NOT_FOUND, NOT_NULL_ASSERT_VIOLATION, NOT_NULL_CONSTRAINT_VIOLATION, NO_HANDLER_FOR_UDAF, NULLABLE_COLUMN_OR_FIELD, NULLABLE_...