mongodb inner join

Type DefinitionThe inner connection only connects the matched rows.The left Outer Join contains all rows in the left table (no matter whether the table on the right has rows matching them) and all matched rows in the right tableThe right Outer Join contains all rows in the right table (no matter whether the left table has rows matching them) and all matched rows

Data Table connection (left join, right join, inner join, Cartesian) -- Query analyzer execution:-- Create Table Table1, Table2:Create Table Table1 (ID int, name varchar (10 ))Create Table Table2 (ID int, score INT)Insert into Table1 select 1, 'lil'Insert into Table1 select 2, 'zhang'Insert into Table1 select

First, take a look at some of the simplest examples. Example Table AAid Adate1 A12 A23 A3 TableB Bid Bdate1 B12 B24 B4Two table a,b connected, to remove fields with the same IDSELECT * from a INNER join B on a.aid = B.bid This is the only matching data to be fetched.At this point, the removal is:1 A1 B12 A2 B2 So the left join means:SELECT * from a LEFT

SQL left join, right join, and inner join Today, I chatted with a friend about a small problem in their company. As follows: Table A device table stores MAC addresses, provinces, cities, and zones.Table B Software Table, which stores MAC addresses and software names.You can query the Software List by province, city, or

left join is exactly the opposite, this time it is based on the right table (B), where a table is not enough to fill with null. 4. Inner Join Example: 4.1Select * from A inner join B on a.aid = B.bid; This shows only the records of A.aid = B.bid. This shows that

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Inner join on, left join on, right join on, innerjoin 1. Definition: Inner join: only records with equal join fields in two tables are returned. Left

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Label:First borrow the official explanation under: Inner JOIN (equivalent connection): Returns only rows with the same junction field in two tables; Left join: Returns records that include all records in the left table and the equivalent of the junction fields in the right table; Right join: Returns records that includ

The LEFT join is a shorthand for the left outer join, and the left join defaults to the outer property. Inner JoinThe Inner join logical operator returns each row that satisfies the first (top) input and the second (bottom) input

Label:The difference between inner join, outer join, and Cross join in SQL many people do not know, I also ask, just look for information to look at, with their previous understanding, if you use join table, the case of defects is inner