ClickHouse是俄罗斯的Yandex于2016年开源的列式存储数据库(DBMS),使用C++语言编写,主要用于在线分析处理查询(OLAP),能够使用SQL查询实时生成分析数据报告。 OLAP(On-Line Analytical Processing)翻译为联机分析处理,专注于分析处理,从对数据库操作来看,OLAP是对数据的查询; OLTP(on-line transaction processing)翻译为联机...
(1) SIMPLE(简单SELECT,不使用UNION或子查询等) (2) PRIMARY(子查询中最外层查询,查询中若包含任何复杂的子部分,最外层的select被标记为PRIMARY) (3) UNION(UNION中的第二个或后面的SELECT语句) (4) DEPENDENT UNION(UNION中的第二个或后面的SELECT语句,取决于外面的查询) (5) UNION RESULT(UNION的结果,uni...
case T_RecursiveUnion: pname = sname = "Recursive Union"; break; case T_BitmapAnd: pname = sname = "BitmapAnd"; break; case T_BitmapOr: pname = sname = "BitmapOr"; break; case T_NestLoop: pname = sname = "Nested Loop"; break; case T_MergeJoin: pname = "Merge"; /* ...
the MySQL optimizer considers many techniques to efficiently performthe lookups involved in an SQL query. A query on a huge table can be performedwithout reading all the rows; a join involving several tables can be performedwithout comparing every combination of rows. The set of operations...
Answer to: List the private solutions that can be used to deal with externalities. Explain in detail including proper graphs, diagrams and figures...
(1)SIMPLE:除子查询或者UNION 之外的其他查询; (2)PRIMARY:子查询中的最外层查询,注意并不是主键查询; (3)UNION:UNION 语句中第二个SELECT 开始的后面所有SELECT,第一个SELECT 为PRIMARY (4)UNION RESULT:UNION 中的合并结果; (5)SUBQUERY:子查询内层查询的第一个SELECT,结果不依赖于外部查询结果集; ...
(1)SIMPLE:除子查询或者UNION 之外的其他查询; (2)PRIMARY:子查询中的最外层查询,注意并不是主键查询; (3)UNION:UNION 语句中第二个SELECT 开始的后面所有SELECT,第一个SELECT 为PRIMARY (4)UNION RESULT:UNION 中的合并结果; (5)SUBQUERY:子查询内层查询的第一个SELECT,结果不依赖于外部查询结果集; ...
后面的SELECT语句,取决于外面的查询 UNION RESULT : UNION的结果 SUBQUERY: 子查询中的第一个SELECTDEPENDENT SUBQUERY : 子查询中的第个SELECT,取决于外面的查询 DERIVED:派生表的SELECT(FROM子句的查询) table: 显示这条sql涉及到的那些表时不是真实的表名字,看到的是derivedx(x是个数字,我的理解是第几...
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The economy of a region is defined as the phase or state which prevails in that region or country. The economy depends on the quantity of production and consumption, the per capita income, the import and export quantity, exchange rate, and more. Financial, social, and economic factors decide...