Usage of MySQL’s “IF EXISTS”
You cannot use IF control block OUTSIDE of functions. So that affects both of your queries. Turn the EXISTS clause into a subquery instead within an IF function In fact, booleans are returned as 1 or 0
Database
Error 1046 No database Selected, how to resolve?
You need to tell MySQL which database to use: before you create a table. In case the database does not exist, you need to create it as: followed by:
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint
It occurred because you tried to create a foreign key from tblDomare.PersNR to tblBana.BanNR but/and the values in tblDomare.PersNR didn’t match with any of the values in tblBana.BanNR. You cannot create a relation which violates referential integrity.
SELECT * FROM multiple tables. MySQL
What you do here is called a JOIN (although you do it implicitly because you select from multiple tables). This means, if you didn’t put any conditions in your WHERE clause, you had all combinations of those tables. Only with your condition you restrict your join to those rows where the drink id matches. But there are still X … Read more
SQL Server: Invalid Column Name
Whenever this happens to me, I press Ctrl+Shift+R which refreshes intellisense, close the query window (save if necessary), then start a new session which usually works quite well.
Exit a SQLite 3 database
I have an SQLite 3 database in SUSE Linux. It’s stuck at the command prompt like so: How do I exit out of the database?
ORA-01653: unable to extend table by in tablespace ORA-06512
Just add a new datafile for the existing tablespace To find out the location and size of your data files:
Simple way to calculate median with MySQL
In MariaDB / MySQL: Steve Cohen points out, that after the first pass, @rownum will contain the total number of rows. This can be used to determine the median, so no second pass or join is needed. Also AVG(dd.val) and dd.row_number IN(…) is used to correctly produce a median when there are an even number of records. Reasoning: Finally, MariaDB 10.3.3+ … Read more
Mysql command not found in OS X 10.7
This is the problem with your $PATH: /usr/local//usr/local/mysql/bin/private/var/mysql/private/var/mysql/bin. $PATH is where the shell searches for command files. Folders to search in need to be separated with a colon. And so you want /usr/local/mysql/bin/ in your path but instead it searches in /usr/local//usr/local/mysql/bin/private/var/mysql/private/var/mysql/bin, which probably doesn’t exist. Instead you want ${PATH}:/usr/local/mysql/bin. So do export PATH=${PATH}:/usr/local/mysql/bin. If you want this to be run … Read more
SQL Server Insert if not exists
instead of below Code replace with Updated : (thanks to @Marc Durdin for pointing) Note that under high load, this will still sometimes fail, because a second connection can pass the IF NOT EXISTS test before the first connection executes the INSERT, i.e. a race condition. See stackoverflow.com/a/3791506/1836776 for a good answer on why even wrapping in a … Read more