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Tag: mysql

Does using “LIMIT 1” speed up a query on a primary key?

If I have a primary key of say id and I do a simple query for the key such as, Will it find one row and then stop looking as it is a primary key, or would it be better to tell mysql to limit its select by using LIMIT 1? For instance: Answer Does using “LIMIT 1” speed up

Using SELECT for simple BOOLEAN evaluation

I want to test some evaluations without working on any table. For example, you can write I want to achieve something like this: I know that most engines don’t have the concept of a boolean data type, but I don’t know how their internal work (even if I guess everything <> 0 is true, like in C…

left join returning more than expected

Using the following query table1 returns 16 rows and table2 returns 35 rows. I was expecting the above query to return 16 rows because of the left join, but it is returning 35 rows. right join also returns 35 rows Why is this happening and how do I get it to return 16 rows? Answer LEFT JOIN can return multipl…

How can I return pivot table output in MySQL?

If I have a MySQL table looking something like this: company_name action pagecount ——————————- Company A PRINT 3 Company A PRINT 2 Company A PRINT 3 Company B EMAIL Company B PRINT 2 Company B PRINT 2 Company B PRINT 1 Company A PRINT 3 Is it possibl…

Get number of values that only appear once in a column

Firstly, if it is relevant, I’m using MySQL, though I assume a solution would work across DB products. My problem is thus: I have a simple table with a single column. There are no constraints on the column. Within this column there is some simple data, e.g. I need to get the number/count of values that …

Doctrine 2 Query Builder abs Function

This Work: This Don’t Work: The Error: Syntax Error] line 0, col 118: Error: Expected end of string, got ‘(‘ The native doctrine function abs work only on a select part of statment and don’t work on order by part. Obs: 1-) Im avoiding to use NativeQuery. 2-) u.code is a varchar fild on…