What is a SQL JOIN, and what are the different types?
First and foremost: JOINs are cartesian products This is why Venn diagrams explain them so inaccurately, because a JOIN creates a cartesian product between the two joined tables. …
What's the difference between INNER JOIN, LEFT JOIN, RIGHT …
FULL JOIN: combines the results of both left and right outer joins. The joined table will contain all records from both the tables and fill in NULLs for missing matches on either side. SELF JOIN: …
How can I do an UPDATE statement with JOIN in SQL Server?
I need to update this table in SQL Server with data from its 'parent' table, see below: Table: sale id (int) udid (int) assid (int) Table: ud id (int) assid (int) sale.assid contains the correct
sql - Condition within JOIN or WHERE - Stack Overflow
The question and solutions pertain specifically to INNER JOINs. If the join is a LEFT/RIGHT/FULL OUTER JOIN, then it is not a matter of preference or performance, but one of correct results. …
SQL JOIN where to place the WHERE condition? - Stack Overflow
If a filter enters in a JOIN condition functionally (i.e. it is an actual join condition, not just a filter), it must appear in the ON clause of that join. Worth noting: If you place it in the WHERE clause …
mysql - sql joins as venn diagram - Stack Overflow
Dec 22, 2012 · I've had trouble understanding joins in sql and came upon this image which I think might help me. The problem is that I don't fully understand it. For example, the join in the top …
sql - How to do join on multiple criteria, returning all combinations ...
May 28, 2014 · I am willing to bet that this is a really simple answer as I am a noob to SQL. Given: table1 has column 1 (criteria 1) column 2 (criteria 2) column 3 (metric 1) table2 has column 1 …
How to Improve Query Performance with many JOINs
"joins" is the killer for performance, the bigger your data is, the more pain you will feel; Try to get rid of joins, not try to improve query performance by keeping joins unless you have to.
sql - Oracle " (+)" Operator - Stack Overflow
Oct 26, 2010 · That's Oracle specific notation for an OUTER JOIN, because the ANSI-89 format (using a comma in the FROM clause to separate table references) didn't standardize OUTER …
Does the join order matter in SQL? - Stack Overflow
Mar 8, 2012 · Most joins using the JOIN keyword are flattened into simple joins, so the optimizer chooses their join order. The optimizer does not choose the join order for outer joins; it uses …