MySQL supports generated columns. If you’re not sure whether a table has a generated column or not, you can check it using any of the following methods.
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How to Return the Expiry Time as a Unix Timestamp in Redis
In Redis, we have several options for returning the expiry time of a key. One option from Redis 7.0.0 and above is to return it as a Unix timestamp.
When returning the expiry as a Unix timestamp, we can have it returned in seconds or milliseconds. To return it in seconds, we can use the EXPIRETIME command. To return it in milliseconds, we can use the PEXPIRETIME command.
2 Ways to Set a Redis Key Only When it Doesn’t Already Exist
In Redis, it’s possible to set a key only if it doesn’t already exist. As with most things, there’s more than one way to do this.
Continue readingHow to Set an Expiry Only When the New Expiry is Greater Than the Existing Expiry in Redis
Redis 7.0.0 introduced some potentially useful options for setting timeouts on keys. One of these is the GT option, which allows us to set the expiry only if the new expiry is greater than the existing one.
The GT option is available for commands such as EXPIRE, EXPIREAT, PEXPIRE, and PEXPIREAT.
How to Get the First Day of the Month in SQL
Below are examples of using SQL to return the first day of the month across various DBMSs.
This could be the first day of the current month, or the first day of a month based on a given date.
Continue reading6 Ways to Set a String in Redis
When working with Redis, we have a number of options for setting keys that store string values.
Here are six ways to set a string value in Redis.
Continue reading2 Ways to Remove a Key’s Expiry in Redis
A Redis key can have an optional timeout, which makes the key expire after a certain amount of time, or at a certain time. We can use a couple of methods to remove any timeout associated with a key.
Here are two ways to remove a key’s expiry in Redis.
Continue readingHow to Update a Key and Return its Old Value in a Single Operation in Redis
When using the SET command to set a key in Redis, we can use the GET option to return its old value. This allows us to update the value of a key while returning the value that we’re replacing it with.
Note that this option was introduced in Redis 7.0.0, so if it doesn’t work, check your Redis version. If using an earlier version, try the GETSET command instead (which is deprecated from Redis version 6.2.0).
Subtract Months from a Date in SQLite
In SQLite, we can use the DATE() function to subtract one or more months from a date.
For datetime values, we can use the DATETIME() function.
4 Ways to Decrement a Key in Redis
In Redis, we have several options for decrementing a key. By this, I mean, reducing the value of a key by one or more. For example, if we set a key to 15, we can decrement it by 1 to make 14. Or we can increment it by whatever amount we desire.
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