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。
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...
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...
PostgreSQL使用WITH xxx AS()查询,使用Page中的OrderItem排序,拼接分页sql时会把WITH xxx AS()这段SQL忽略,导致查不到此表抛出了异常; 如果不使用OrderItem排序,正常不会出现此问题; 重现步骤(如果有就写完整) 代码 //sevice调用 @Autowired private AreaBaseDao areaBaseDao; public IPage<AreaBaseEntity> test...
那么是否有别的实现方式呢?这个时候就可以使用 PostgreSQL 的WITH子句了: WITHdep_withAS(SELECT"id","name","parent_id"FROMdepartmentWHERE"id"=10)SELECTdep."name"FROMdepartmentdepJOINdep_withONdep_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,的确是这样。但是...
PostgreSQL没有从WITH中删除行。。。AS UPDATE子句 我想编写一个执行UPDATE的查询,如果结果行与约束匹配,则执行DELETE。 为了测试,我有下表: # CREATE TABLE counts (id BIGSERIAL PRIMARY KEY, count BIGINT NOT NULL); # INSERT INTO counts (count) VALUES (5), (1);...
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...
in PostgreSQL, unlimited text and varchar have some performance advantage over the limited types. Use the latter if you really have a limit. With varchar(255) the case is usually 'We don't know how long it can be, but definitely not that long'. Email addresses are usually consider...
postgresql Share Follow asked Apr 17, 2016 at 17:13 wjv 2,55811 gold badge2020 silver badges2222 bronze badges Add a comment 1 Answer Sorted by: 2 As the uuid in the node table is generated by a sequence, the only way I can think of is to flip the order of i...
i.e. Anonymous user would not be able to create a role, but anonymous user would be able to execute function (with valid security JWT as input), and indirectly create roles through the function. postgresql permissions functions role Share Improve this question Follow edited ...