Database Management Systems
The Redis GETDEL command gets the value of a given key, then deletes that key. It’s similar to the GET command, except that it deletes the key on success (the GET command doesn’t delete the key – it only returns its value).
An error is returned if the value stored at key is not a string.
The GETDEL command was introduced in Redis 6.2.0.
In Redis, the DEL command removes one or more keys. If a specified key doesn’t exist, it’s ignored.
In Redis, the LCS command implements the longest common subsequence algorithm.
The longest common subsequence algorithm finds the longest subsequence common to all sequences in a set of sequences. Note that this is different to the longest common string algorithm (also known as the longest common substring algorithm), which requires that matching characters in the string are contiguous. The longest common subsequence algorithm, on the other hand, doesn’t require matching characters to be contiguous.
The LCS command was introduced in Redis 7.0.0.
Continue readingThe Redis GETEX command enables us to get the value of a key, then set the key’s expiration. We can also use it to remove any existing expiration associated with the key.
In MariaDB, the NVL2() function allows us to replace a value with another value, the new value being determined by whether or not the initial value is null.
It’s similar to the NVL() function, except that NVL2() accepts three arguments instead of two. This allows us to specify a different value to return in the event the first argument is not null.
Here are two quick and easy options to find out what version of the Redis client (redis-cli) you’re using.
Here are four quick and easy ways to find out what version of Redis you’re using.
Continue readingThe Redis SETNX command sets a key to a given value, but only if the key doesn’t already exist. If the key already holds a value, no operation is performed.
Note: The SET command can do the same thing, and it’s possible that the SETNX command may be deprecated at some point. Therefore, it’s probably a good idea to use SET instead of SETNX if possible.
Below are examples of using SQL to return the last day of the month across various DBMSs.
This could be the last day of the current month, or the last day of a month based on a given date.
Continue readingIn Redis, the MSETNX command allows us to set multiple keys at once, but only if none of them exist.
This allows us to set multiple keys representing different fields of a single logical object in a way that ensures that either all the fields are set, or none are set.
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