outer-join

问题 I am checking some old SQL Statements for the purpose of documenting them and probably enhancing them. The DBMS is Oracle I did not understand a statement which read like this: select ... from a,b where a.id=b.id(+) I am confused about the (+) operator, and could not get it at any forums... (searching for + within quotes didn\'t work either). Anyway, I used \'Explain Plan\' of SQLDeveloper and I got an output saying that HASH JOIN, RIGHT OUTER , etc. Would there be any difference if I remove

问题 I have the following SQL, which I am trying to translate to LINQ: SELECT f.value FROM period as p LEFT OUTER JOIN facts AS f ON p.id = f.periodid AND f.otherid = 17 WHERE p.companyid = 100 I have seen the typical implementation of the left outer join (ie. into x from y in x.DefaultIfEmpty() etc.) but am unsure how to introduce the other join condition ( AND f.otherid = 17 ) EDIT Why is the AND f.otherid = 17 condition part of the JOIN instead of in the WHERE clause? Because f may not exist

问题 I have a list of people\'s ID and their first name, and a list of people\'s ID and their surname. Some people don\'t have a first name and some don\'t have a surname; I\'d like to do a full outer join on the two lists. So the following lists: ID FirstName -- --------- 1 John 2 Sue ID LastName -- -------- 1 Doe 3 Smith Should produce: ID FirstName LastName -- --------- -------- 1 John Doe 2 Sue 3 Smith I\'m new to LINQ (so forgive me if I\'m being lame) and have found quite a few solutions for

问题 This question already has answers here : What is the difference between “INNER JOIN” and “OUTER JOIN”? (25 answers) Closed 4 years ago . What\'s the difference between INNER JOIN , LEFT JOIN , RIGHT JOIN and FULL JOIN in MySQL ? 回答1: Reading this original article on The Code Project will help you a lot: Visual Representation of SQL Joins. Also check this post: SQL SERVER – Better Performance – LEFT JOIN or NOT IN?. Find original one at: Difference between JOIN and OUTER JOIN in MySQL. 回答2:

问题 I want to do a Full Outer Join in MySQL. Is this possible? Is a Full Outer Join supported by MySQL? 回答1: You don't have FULL JOINS on MySQL, but you can sure emulate them. For a code SAMPLE transcribed from this SO question you have: with two tables t1, t2: SELECT * FROM t1 LEFT JOIN t2 ON t1.id = t2.id UNION SELECT * FROM t1 RIGHT JOIN t2 ON t1.id = t2.id The query above works for special cases where a FULL OUTER JOIN operation would not produce any duplicate rows. The query above depends on

问题 Also how do LEFT JOIN , RIGHT JOIN and FULL JOIN fit in? 回答1: Assuming you're joining on columns with no duplicates, which is a very common case: An inner join of A and B gives the result of A intersect B, i.e. the inner part of a Venn diagram intersection. An outer join of A and B gives the results of A union B, i.e. the outer parts of a Venn diagram union. Examples Suppose you have two tables, with a single column each, and data as follows: A B - - 1 3 2 4 3 5 4 6 Note that (1,2) are unique