sql semi join

Often used in the work, although the same year in the database principles of the course, but the basic has been returned to the teacher. Work for so many years, feel oneself in study backwards a lot, ashamed. This post, as a SQL related knowledge of the finishing paste.1, semi-join (half Connection) (from: Http://wiki.answers.com/Q/What_is_semi_join_in_SQL)A

For example: Hive> select * From zz0;111111222222888888Hive> select * From zz1;111111333333444444888888 Hive> select * From zz0 join zz1 on zz0.uid = zz1.uid;111111 111111888888 888888Hive> select * From zz0 left Outer Join zz1 on zz0.uid = zz1.uid;111111 111111222222 null888888 888888Hive> select * From zz0 right Outer Join zz1 on zz0.uid = zz1.uid;Null111111

the same as that in the previous example! 4: Inner join or join; It is the record that the returned field ID exists in both the table votemaster and voter.5: Cross join (full join) with no where Condition A cross join without a where clause will generate the Cartesian produ

When two tables are joined, if the data row in table 1 appears in the result set and needs to be judged by at least one matching row of data appearing in table 2, in this case, a semi join occurs, and the inverse join is a partially joined complement, which is used as a common method of joining in the database such as nested The options for the Loops,merge SORT

Table join methods include join, semi-join, outer-join, and anti-join; Table join implementation methods such as nested loop, merge, and hash. This article briefly introduces table

without the where ConditionA cross join without a where clause will generate the Cartesian product of the table involved in the join. The number of rows in the first table multiplied by the number of rows in the second table is equal to the size of the Cartesian result set. (Table 1 and Table 2 generate 6*3 = 18 Records)Equivalent to select VM. ID, VM. votetitle, vt. IP from votemaster as Vm, voter as vt

following commands in the query Analyzer: 1. External Connection1. Concept: including left Outer Join, right Outer Join or complete external join 2. Left join: left join or left Outer Join(1) The result set of the left Outer

About semi-join in Oracle Table join is particularly important in SQL statements. External connections, internal connections, semi-connections, anti-connections, and other connections, there are still a lot of details in a simple connection. It is also important for

SQL join is used to query data from these tables based on the relationship between the columns in two or more tables.Join and KeySometimes in order to get the complete result, we need to get the results from two or more tables. We need to execute the join.Tables in the database can be linked by keys. The primary key (Primary key) is a column, and the value of each row in the column is unique. In the table,

Tags: style blog http color using OS IO data1. Background informationWhat is Semi-join?The so-called Semi-join refers to the semi-join subquery. When a table finds a matching record in another table, the

Http://www.linuxidc.com/Linux/2015-05/117523.htm 1. Background informationWhat is Semi-join?The so-called Semi-join refers to the semi-join subquery. When a table finds a matching record in another table, the

Execute the following hive sql:SELECT * from Trackinfo where ds= $date and session_id in (select session_id from Rcmd_track_path where ds= $date and Add_ca Rt_flag>0 and Product_id>0);The following error is indicated:Failed:parseexception line 2:39 cannot recognize input near ' select ' session_id "from" in expression specificationCause analysis solutions are as follows:Hive does not support the use of in subqueries, consider replacing in with the left semi