I'm pretty new to Python and am completely confused by .join() which I have read is the preferred method for concatenating strings. I tried: strid = repr(595) print array.array('c', random.sample(
The fact that when it says INNER JOIN, you can be sure of what it does and that it's supposed to be just that, whereas a plain JOIN will leave you, or someone else, wondering what the standard said about the implementation and was the INNER/OUTER/LEFT left out by accident or by purpose.
Left Join and Left Outer Join are one and the same. The former is the shorthand for the latter. The same can be said about the Right Join and Right Outer Join relationship. The demonstration will illustrate the equality. Working examples of each query have been provided via SQL Fiddle. This tool will allow for hands on manipulation of the query. Given Left Join and Left Outer Join Results
This JOIN combines LEFT OUTER JOIN and RIGHT OUTER JOIN. It returns rows from either table when the conditions are met and returns NULL value when there is no match. In other words, OUTER JOIN is based on the fact that: ONLY the matching entries in ONE OF the tables (RIGHT or LEFT) or BOTH of the tables (FULL) SHOULD be listed.
INNER JOIN gets all records that are common between both tables based on the supplied ON clause. LEFT JOIN gets all records from the LEFT linked and the related record from the right table ,but if you have selected some columns from the RIGHT table, if there is no related records, these columns will contain NULL.
Inner join is a join that combined tables based on matching tuples, whereas outer join is a join that combined table based on both matched and unmatched tuple. Inner join merges matched row from two table in where unmatched row are omitted, whereas outer join merges rows from two tables and unmatched rows fill with null value.
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 instead, the performances are the same if the join is INNER, otherwise it differs. As mentioned in the comments it does not really matter since anyway the outcome is different. Placing the ...
A CROSS JOIN produces a cartesian product between the two tables, returning all possible combinations of all rows. It has no ON clause because you're just joining everything to everything. A FULL OUTER JOIN is a combination of a LEFT OUTER and RIGHT OUTER join. It returns all rows in both tables that match the query's WHERE clause, and in cases where the ON condition can't be satisfied for ...
