How to create a foreign key in phpmyadmin
You can do it the old fashioned way… with an SQL statement that looks something like this This assumes the keys already exist in the relevant table
database
MySQL equivalent of DECODE function in Oracle
You can use IF() where in Oracle you would have used DECODE().
Can I have multiple primary keys in a single table?
A Table can have a Composite Primary Key which is a primary key made from two or more columns. For example: Update: Here is a link with a more detailed description of composite primary keys.
Cannot attach the file *.mdf as database
Take a look at this: Entity Framework don’t create database I would try giving the database a different name. Sometimes you can run into problems with SQL Express when trying to create a database with the same name a second time. There is a way to fix this using SQL Server Management Studio but it’s … Read more
OperationalError: database is locked
From django doc: SQLite is meant to be a lightweight database, and thus can’t support a high level of concurrency. OperationalError: database is locked errors indicate that your application is experiencing more concurrency than sqlite can handle in default configuration. This error means that one thread or process has an exclusive lock on the database … Read more
Database vs File system storage
A database is generally used for storing related, structured data, with well defined data formats, in an efficient manner for insert, update and/or retrieval (depending on application). On the other hand, a file system is a more unstructured data store for storing arbitrary, probably unrelated data. The file system is more general, and databases are … Read more
How do I reset a sequence in Oracle?
Here is a good procedure for resetting any sequence to 0 from Oracle guru Tom Kyte. Great discussion on the pros and cons in the links below too. From this page: Dynamic SQL to reset sequence valueAnother good discussion is also here: How to reset sequences?
Difference between database and schema
A database is the main container, it contains the data and log files, and all the schemas within it. You always back up a database, it is a discrete unit on its own. Schemas are like folders within a database, and are mainly used to group logical objects together, which leads to ease of setting … Read more
Postgres Error: More than one row returned by a subquery used as an expression
Technically, to repair your statement, you can add LIMIT 1 to the subquery to ensure that at most 1 row is returned. That would remove the error, your code would still be nonsense. Practically, you want to match rows somehow instead of picking an arbitrary row from the remote table store to update every row of your local table customer.Your rudimentary question … Read more
sqlite3.OperationalError: unable to open database file
Django NewbieMistakes PROBLEM You’re using SQLite3, your DATABASE_NAME is set to the database file’s full path, the database file is writeable by Apache, but you still get the above error. SOLUTION Make sure Apache can also write to the parent directory of the database. SQLite needs to be able to write to this directory. Make … Read more