product,SUM(quantity)ASproduct_units,SUM(amount)ASproduct_salesFROMordersWHEREregionIN(SELECTregionFROMtop_regions)GROUPBYregion, product; with语句与全连接 WITHRECURSIVE included_parts(sub_part, part, quantity)AS(SELECTsub_part, part, quantityFROMpartsWHEREpart='our_product'UNIONALLSELECTp.sub_part, p...
用with as ,其实跟直接用子查询效率上没有什么区别;而用临时表与永久表相似,数据是真是存储到数据库里,相当于第二次直接关联的是一个小表,查询效率大大提高。 4使用场景 with as 适用于:为了增加代码可读性,且没有很多复杂的关联子查询。 临时表适用于:有很多复杂的关联子表查询。
并且WITH子句本身也可以被附加到一个主语句,主语句也可以是SELECT、INSERT、UPDATE或DELETE。 WITH regional_sales AS ( SELECT region, SUM(amount) AS total_sales FROM orders GROUP BY region ), top_regions AS ( SELECT region FROM regional_sales WHERE total_sales > (SELECT SUM(total_sales)/10 FROM...
SELECT t.* FROM test AS t ORDER BY id DESC LIMIT 10 offset 0; 报错信息 ### SQL: SELECT t.* FROM test AS t ORDER BY id DESC limit ? offset ? ### Cause: org.postgresql.util.PSQLException: ERROR: relation "test" does not exist liguanqiao创建了任务5年前 liguanqiao将关联仓库设置为...
这个时候就可以使用 PostgreSQL 的 WITH 子句了: WITH dep_with AS ( SELECT "id", "name", "parent_id" FROM department WHERE "id" = 10 ) SELECT dep."name" FROM department dep JOIN dep_with ON dep_with."parent_id" = dep."id" 这么一看好像使用 WITH 子句的代码量并没有比前两种写法少呀...
WITH RECURSIVE t(n) AS ( VALUES (1) UNION ALL SELECT n+1 FROM t WHERE n < 100 ) SELECT sum(n) FROM t; 其中RECURSIVE是递归的关键字,一定得有这个标识,PostgreSql才知道这个with语句是做递归操作。 需要说明的是union all的选择可以使union,与一般使用union和union all一样前者是去重的,后者是包含...
f (2 rows) 多个code的场景 digoal=> with recursive sub as ( SELEC id,code,coalesce(case when length(substring(code,1,length(code)-3))=0 then null else substring(code,1,length(code)-3) end,'root') parcode, extend FRO tbl_role WHE code in ('001005','001003') union SELEC d.* FR...
使用AS语法,可以给查询结果列设置别名,方便后续的引用。 示例代码: 代码语言:txt 复制 var query = from p in dbContext.Persons where p.Age > 18 select new { FullName = p.FirstName + " " + p.LastName, p.Age }; // 使用AS给查询结果列设置别名 var queryWithAs = from p in dbContext.Pe...
This can occur with B-tree indexes in PostgreSQL under certain uncommon access patterns. REINDEX provides a way to reduce the space consumption of the index by writing a new version of the index without the dead pages. A storage parameter (such as fillfactor) has been changed for...
localhost:ytt>WITHrecursivetmp(a)AS->(SELECT->1->UNION->ALL->SELECT->a+2->FROM->tmp->WHEREa<100)->DELETEFROMy1WHEREidIN(TABLEtmp);QueryOK,50rowsaffected(0.02sec)localhost:ytt>table y1 limit10;+---+---+---+|id|r1|log_date|+---+---+---+|2|6|2019-05-16||4|8|2015-12...