1、INNER JOIN:如果表中有至少一个匹配,则返回行; 2、LEFT JOIN:即使右表中没有匹配,也从左表返回所有的行; 3、RIGHT JOIN:即使左表中没有匹配,也从右表返回所有的行; 4、FULL JOIN:只要其中一个表中存在匹配,则返回行 。 三、如何使用各种join (一)准备测试数据 测试的数据很简单,依旧拿来在课堂上,书...
为了更直观的了解以上join方式,我们通过俩个测试表来进行测试,首先是建表语句: create table U ( name varchar2(20), gender varchar2(10) ); create table D( name varchar2(20), sal number(6,0) ); insert into U values('tom','male'); insert into U values('jerry','male'); insert into ...
A join is a query that combines rows from two or more tables, views, or materialized views. Oracle Database performs a join whenever multiple tables appear in the FROM clause of the query. The select list of the query can select any columns from any of these tables. If any two of thes...
它的语法树、优化后的物理计划,以及最终执行计划(红框标明的是 JOIN 部分)如下,可以看到算子已经由之前的 Join 变成了 IntervalJoin: Interval Join 计划 在运行时,Flink 会调用org.apache.flink.table.runtime.operators.join.interval.TimeIntervalJoin执行具体的关联操作,具体的 JOIN 逻辑在org.apache.flink.table....
关于sql语句中的连接(join)关键字,是较为常用而又不太容易理解的关键字,下面这个例子给出了一个简单的解释 –建表user1,user2: table1 : create table user2(id int, user_name varchar(10), over varchar(10)); insert into user1 values(1, ‘tangseng', ‘dtgdf'); ...
CREATE TABLE `student` (`idStudent` int(11) DEFAULT NULL, `name` varchar(50) DEFAULT NULL, `idSupervisor` int(11) DEFAULT NULL) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3; And then, fill it with the following data: INSERT INTO dbo.student (`idStudent`, `name`, `idSupervisor`) ...
为了更直观的了解以上join方式,我们通过俩个测试表来进行测试,首先是建表语句: create table U ( name varchar2(20), gender varchar2(10) ); create table D( name varchar2(20), sal number(6,0) ); insert into U values('tom','male'); ...
ClickHouse高级数据查询SQL: WITH/JOIN/IN/INTO OUTFILE/嵌套子查询/交并差计算等,本文目录1.1.SQL概述1.1.1.SQL简史1.1.2.SQL概述1.1.3.ClickHouseSQL
CREATE TABLE sink_table ( s_id BIGINT, s_params STRING, c_id BIGINT, c_params STRING ) WITH ( 'connector' = 'print' ); -- 流的 INNER JOIN,条件为 log_id INSERT INTO sink_table SELECT show_log_table.log_id as s_id, show_log_table.show_params as s_params, ...
More on SQL JOIN SQL Self JOIN In SQL, the SelfJOINoperation allows us to join a table with itself, creating a relationship between rows within the same table. Let's look at an example. SELECTC1.first_nameASFirstPerson, C2.first_nameASSecondPerson, C1.countryFROMCustomers C1, Customers ...