Database Management Systems
In MySQL, CAST() is a built in function that converts a value to another data type. It takes a value of one type and returns a value of the specified type.
You provide the value as an argument when you call the function, as well as the type that you’d like it converted to.
CAST() works similar to CONVERT(), except that the syntax used is slightly different.
If you’re getting error 1298 that reads something like “ERROR 1298 (HY000): Unknown or incorrect time zone: ‘UTC’” in MySQL, it’s probably because you’re specifying a time zone name, but your MySQL installation hasn’t yet been configured for named time zones.
To fix this issue, be sure that your MySQL installation has been configured for named time zones.
If you’re getting an error that reads something like “lastval is not yet defined in this session” when calling the lastval() function in PostgreSQL, it’s probably because nextval() hasn’t yet been called in the current session.
If you want to avoid this error, only call the lastval() function when you know that nextval() has been called at least once in the current session.
If you’re getting error msg 237 that reads There is insufficient result space to convert a money value to int, it’s because you’re trying to convert a money value to an integer but the number’s too big to fit into an integer.
To fix this issue, make sure you convert the value to a data type that can handle the size of the number that you’re trying to convert.
In Redis, the ZLEXCOUNT command returns the number of elements in a sorted set with a value between two given values. It can be used when we force lexicographical ordering by applying the same score to all members of a sorted set.
In MySQL, the LAST_INSERT_ID() function returns the first automatically generated value successfully inserted for an AUTO_INCREMENT column as a result of the most recently executed INSERT statement.
It can also be called with an argument, in which case, it returns the value of the expression and the next call to LAST_INSERT_ID() will return the same value.
If you’re getting an error that reads something like “Cannot DROP SEQUENCE ‘Sequence2’ because it is being referenced by object ‘DF__Dogs__DogId__6C190EBB’“, it could be because you’re trying to drop a sequence object that’s referenced by a DEFAULT constraint.
Sequences that are referenced by a DEFAULT constraint can’t be dropped until the DEFAULT constraint is dropped.
Therefore, to fix this issue, drop the DEFAULT constraint first.
Below are seven functions we can use to extract the hours, minutes, seconds, and microseconds from a time value in MySQL.
In PostgreSQL, we can use the generate_series() function to return a series of values between a given start and stop point. This can be a series of numbers or a series of timestamps.
The function returns a set containing the series.
In MySQL, the ICU_VERSION() function returns the version of the International Components for Unicode (ICU) library used to support regular expression operations.
The ICU_VERSION() function is primarily intended for use in test cases.