Database Management Systems
If 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.
If you want to use named time zones in MySQL, you’ll need to make sure they’ve been configured.
By “named time zones”, I mean being able to use strings like US/Eastern instead of −04:00 or −05:00 when specifying the time zone. For example, when using the CONVERT_TZ() function.
Here’s how to configure named time zones in MySQL.
If you’re getting error 1045 that reads something like “Access denied for user ‘root’@’localhost’“, it’s because you’re trying to log in to MySQL without the right credentials.
This usually happens when we provide the wrong password. But there could also be another cause. For example, we could be trying to do something as the root user that requires a password, but the root user hasn’t yet had its password set.
To fix this issue, be sure to provide the correct password when connecting to MySQL.