sql case statement
Performance optimization: by reducing the complexity of the SQL queries, the CASE statement can also contribute to optimizing the performance and minimize the execution time, especially when it avoids the need for additional computations and transformations. ...
1.CASE 写法如下: CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 WHEN conditionN THEN resultN ELSE result END; 解释:1)先匹配第一条,不匹配的话继续第二条,如此循环,
In addition to improved readability, case statements also provided an opportunity for optimization. For a more detailed discussion on case statement optimizations check out Switch Statement Performance Consideration for a more thorough discussion. Not to be outdone, T-SQL contains a CASE statement as w...
The SQLCASEstatement evaluates a list of conditions and adds a column with values based on the condition. For example, -- add a new column 'order_volume' in the Orders table-- and flag any order greater than 10000 as 'Large Order'-- and smaller than 10000 as 'Small Order'SELECT*,CASE...
What are the case sensitivity differences between PostgreSQL and SQL Server? Compare index types in PostgreSQL vs. MSSQL 中文:大小写敏感问题比较 PostgreSQL区分大小写来进行字符串比较。LOWER()函数允许用户将字符串转换为全小写以进行比较(还有类似的UPPER()函数)。默认情况下,PostgreSQL将表名和列名转换为小写...
简单CASE 语句 (PL/SQL) 简单CASE 语句尝试将表达式 (称为选择器) 与一个或多个 WHEN 子句中指定的另一个表达式匹配。 发生匹配将导致执行一条或多条相应的语句。 已搜索的 CASE 语句 (PL/SQL) 搜索的 CASE 语句使用一个或多个布尔表达式来确定要执行的语句。
SELECTTOP10qs.last_execution_time, st.textASbatch_text,SUBSTRING(st.TEXT, (qs.statement_start_offset /2) +1, ((CASEqs.statement_end_offsetWHEN-1THENDATALENGTH(st.TEXT)ELSEqs.statement_end_offsetEND- qs.statement_start_offset) /2) +1)ASstatement_text, (qs.total_worker_time /1000) / ...
sql_statement_recompile扩展事件 (XEvent) 报告语句级重新编译。 当任何类型的批处理需要语句级重新编译时,会发生此 XEvent。 这包括存储过程、触发器、即席批处理和查询。 可通过几个接口来提交批处理,这类接口包括 sp_executesql、动态 SQL、“准备”方法或“执行”方法。
Full Optimize还分 Search 0, Search 1, Search 2. Simplification 简单来讲概念就是去重,比如有where条件了,就不用Foreign Key约束,或者join的时候,提前将where条件放到join里面去做限制以减少数据集;Trivial Plan就是不经历full optimize 直接产生执行计划,这里要注意的执行计划属性StatementOptmLevel, 走Trivial Plan...