Launch MySQL Workbench. On the left pane of the welcome window, choose a database to connect to under “Open Connection to Start Querying”. The query window will open. On its left pane, there is a section titled “Object Browser”, which shows the list of databases. (Side note: The terms “schema” and “database” are synonymous in … Read more
UNION puts lines from queries after each other, while JOIN makes a cartesian product and subsets it — completely different operations. Trivial example of UNION: similary trivial example of JOIN:
I’m trying to use MySQL to create a view with the “WITH” clause But it doesn’t seem like MySQL supports this. I thought this was pretty standard and I’m sure Oracle supports this. Is there anyway to force MySQL to use the “WITH” clause? I’ve tried it with the MyISAM and innoDB engine. Both of … Read more
An ORA-01722 error occurs when an attempt is made to convert a character string into a number, and the string cannot be converted into a number. Without seeing your table definition, it looks like you’re trying to convert the numeric sequence at the end of your values list to a number, and the spaces that … Read more
Yes, it a vice versa. It depends on which side of the relationship the entity is present on. For example, if one department can employ for several employees then, department to employee is a one to many relationship (1 department employs many employees), while employee to department relationship is many to one (many employees work … Read more
You could try some sort of COALESCE trick, eg: SELECT COALESCE( CASE WHEN condition1 THEN calculation1 ELSE NULL END, CASE WHEN condition2 THEN calculation2 ELSE NULL END, etc… )
What kind of field is this? The IN operator cannot be used with a single field, but is meant to be used in subqueries or with predefined lists: If you are searching a string, go for the LIKE operator (but this will be slow): If you restrict it so that the string you are searching … Read more
You need to set oracle to listen on all ip addresses (by default, it listens only to localhost connections.) Step 1 – Edit listener.ora This file is located in: Windows: %ORACLE_HOME%\network\admin\listener.ora. Linux: $ORACLE_HOME/network/admin/listener.ora Replace localhost with 0.0.0.0 Step 2 – Restart Oracle services Windows: WinKey + rservices.msc Linux (CentOs):sudo systemctl restart oracle-xe
This part: makes it possible to introduce a variable without the need of a seperate query. So the first query could also be broken down into two queries like this: for instance when used in a stored procedure.