Database Management Systems
In SQLite, ABS() is a built-in scalar function that returns the absolute value of its argument.
The absolute value is the non-negative equivalent of the argument. It can be thought of as the distance from zero that the number resides on the number line, without considering direction.
Continue readingHere are seven ways to check what version of MySQL you’re running.
Continue readingIf you’re getting an error that reads something like “Msg 3728, Level 16, State 1, Line 1
‘DF__Dogs__DogId__6FE99F9F’ is not a constraint“, it’s probably because you’re trying to drop a constraint that isn’t in the database.
To fix this issue, check to make sure the constraint exists before dropping it. Alternatively, use the IF EXISTS clause to drop the constraint only if it exists.
In MySQL, VERSION() is a built-in function that returns the MySQL server version.
The result is a string that uses the utf8mb3 character set. A suffix may also be appended to the version number indicating server build or configuration information.
If you’re getting an error that reads “ERR wrong number of arguments for ‘hrandfield’ command“, it’s probably because you’re not passing any arguments when using the HRANDFIELD command.
The HRANDFIELD command requires at least one argument, and accepts up to three arguments (at the time of writing).
The following table contains a full list of format specifiers that can be used in format strings with functions like DATE_FORMAT(), STR_TO_DATE(), and FROM_UNIXTIME() in MySQL.
When we create a sequence object in SQL Server, we have the option of making it a repeating sequence or a nonrepeating sequence. By repeating I mean, we can have the sequence continually start again once the min/max value has been reached. In other words, we can have the sequence reiterate over and over again.
We can do this with the CYCLE argument.
If you get an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when setting a hash with a command like HSET or HSETNX, it’s probably because you’re trying to set a non-hash key that already exists. In other words, the key already exists, but it doesn’t contain a hash.
To fix this issue, be sure to use these commands on keys that either don’t already exist, or contain a hash.
Continue readingIn MySQL, SESSION_USER() is a synonym for the USER() function. It returns the current MySQL user name and host name, given when connecting to MySQL.
In MySQL, SYSTEM_USER() is a synonym for the USER() function. It returns the current MySQL user name and host name, given when connecting to MySQL.