Difference in MySQL JOIN vs LEFT JOIN
I thought that by not specifying a type of join it was assumed to be a LEFT JOIN. Is this not the case? No, the default join is an INNER JOIN. Here is a visual explanation of SQL joins. Inner join Left join
inner-join
SQL Server – inner join when updating [duplicate]
UPDATE R SET R.status=”0″ FROM dbo.ProductReviews AS R INNER JOIN dbo.products AS P ON R.pid = P.id WHERE R.id = ‘17190’ AND P.shopkeeper=”89137″;
WHERE Clause vs ON when using JOIN
Just be careful of the difference with outer joins. A query where a filter of b.IsApproved (on the right table, Bar) is added to the ON condition of the JOIN: SELECT * FROM Foo f LEFT OUTER JOIN Bar b ON (b.IsApproved = 1) AND (b.BarId = f.BarId); Is NOT the same as placing the … Read more
Mixing ANSI 1992 JOINs and COMMAs in a query
According to this link, you shouldn’t mix up both notations when building up joins. The comma you are using to join memebers as m, telephone as t, and the subsequent calls to inner join, are triggering the unknown column error. To deal with it, use CROSS/INNER/LEFT JOIN instead of commas. Previously, the comma operator (,) … Read more
How to use mysql JOIN without ON condition?
MySQL documentation covers this topic. Here is a synopsis. When using join or inner join, the on condition is optional. This is different from the ANSI standard and different from almost any other database. The effect is a cross join. Similarly, you can use an on clause with cross join, which also differs from standard … Read more
Is having an ‘OR’ in an INNER JOIN condition a bad idea?
This kind of JOIN is not optimizable to a HASH JOIN or a MERGE JOIN. It can be expressed as a concatenation of two resultsets: SELECT * FROM maintable m JOIN othertable o ON o.parentId = m.id UNION SELECT * FROM maintable m JOIN othertable o ON o.id = m.parentId , each of them being … Read more
Multiple INNER JOIN SQL ACCESS
Access requires parentheses in the FROM clause for queries which include more than one join. Try it this way … FROM ((tbl_employee INNER JOIN tbl_netpay ON tbl_employee.emp_id = tbl_netpay.emp_id) INNER JOIN tbl_gross ON tbl_employee.emp_id = tbl_gross.emp_ID) INNER JOIN tbl_tax ON tbl_employee.emp_id = tbl_tax.emp_ID; If possible, use the Access query designer to set up your joins. … Read more
How to get matching data from another SQL table for two different columns: Inner Join and/or Union?
(The following applies when every row is SQL DISTINCT, and outside SQL code similarly treats NULL like just another value.) Every base table has a statement template, aka predicate, parameterized by column names, by which we put a row in or leave it out. We can use a (standard predicate logic) shorthand for the predicate … Read more
Inner join of DataTables in C#
If you are allowed to use LINQ, take a look at the following example. It creates two DataTables with integer columns, fills them with some records, join them using LINQ query and outputs them to Console. DataTable dt1 = new DataTable(); dt1.Columns.Add(“CustID”, typeof(int)); dt1.Columns.Add(“ColX”, typeof(int)); dt1.Columns.Add(“ColY”, typeof(int)); DataTable dt2 = new DataTable(); dt2.Columns.Add(“CustID”, typeof(int)); dt2.Columns.Add(“ColZ”, … Read more