When requests arrive at the application servers simultaneously, weird things can happen. Sometimes, this can also happen if a user...

An association defined with has_many :through will return the same record multiple times if multiple join models for the...

In MySQL comparing zero to a string 0 = "any string" is always true! So when you want to compare a...

When selecting records in a date range, take care not to do it like this: start_date = Date.parse('2007-05...

Note: This applies specifically to MySQL. In PostgreSQL for example, this is not an issue. If you care about performance...

If you want to have an English Ubuntu UI, but still see dates, money amounts, paper formats, etc. in German...

When storing floating-point numbers such as prices or totals in an SQL database, always use a DECIMAL column. Never...

Note: For PostgreSQL you should use advisory locks. For MySQL we still recommend the solution in this card.

CONCAT('foo', 'bar', NULL) = NULL the NULL always wins in MySQL. If you would rather treat NULL as...