MySQL query String contains
Quite simple actually: The % is a wildcard for any characters set (none, one or many). Do note that this can get slow on very large datasets so if your database grows you’ll need to use fulltext indices.
Database
ERROR 2003 (HY000): Can’t connect to MySQL server on localhost (10061)
You don’t need to restart your windows. The easiest way to achieve this is Go to <Extracted folder location>/bin/ Run mysqld (service) close the cmd prompt Run mysql.exe or the better way to do is add the location to PATH environment Variable
SQL SELECT WHERE field contains words
Rather slow, but working method to include any of words: If you need all words to be present, use this: If you want something faster, you need to look into full text search, and this is very specific for each database type.
Using group by on multiple columns
Group By X means put all those with the same value for X in the one group. Group By X, Y means put all those with the same values for both X and Y in the one group. To illustrate using an example, let’s say we have the following table, to do with who is attending what subject at … Read more
INSERT statement conflicted with the FOREIGN KEY constraint – SQL Server
In your table dbo.Sup_Item_Cat, it has a foreign key reference to another table. The way a FK works is it cannot have a value in that column that is not also in the primary key column of the referenced table. If you have SQL Server Management Studio, open it up and sp_help ‘dbo.Sup_Item_Cat‘. See which column that FK … Read more
PostgreSQL “DESCRIBE TABLE”
Try this (in the psql command-line tool): See the manual for more info.
sql query with multiple where statements
You need to consider that GROUP BY happens after the WHERE clause conditions have been evaluated. And the WHERE clause always considers only one row, meaning that in your query, the meta_key conditions will always prevent any records from being selected, since one column cannot have multiple values for one row. And what about the redundant meta_value checks? If a value is allowed to … Read more
Nested select statement in SQL Server
You need to alias the subquery. or to be more explicit
How can I do a FULL OUTER JOIN in MySQL?
You don’t have full joins in MySQL, but you can sure emulate them. For a code sample transcribed from this Stack Overflow question you have: With two tables t1, t2: The query above works for special cases where a full outer join operation would not produce any duplicate rows. The query above depends on the UNION set operator to remove duplicate rows introduced by the query pattern. … Read more
What’s the difference between identifying and non-identifying relationships?
An identifying relationship is when the existence of a row in a child table depends on a row in a parent table. This may be confusing because it’s common practice these days to create a pseudokey for a child table, but not make the foreign key to the parent part of the child’s primary key. Formally, the “right” way … Read more