In Redis, we have several options for incrementing a key. For example, if we set a key to 1, we can increment it by 1 to make 2. Or we can increment it by whatever amount we desire.
Below are four ways to increment a key in Redis.
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Redis SUBSTR Equivalent
Many SQL databases have a SUBSTR() or equivalent function that returns a substring from a specified string.
Redis has a SUBSTR command, but it was deprecated in Redis 2.0.0.
However, Redis also has the GETRANGE command, that basically does the same thing. Basically, anything that was possible with the Redis SUBSTR command, is now possible with the GETRANGE command.
And the GETRANGE command does basically the same thing that most of the SUBSTR() and SUBSTRING() functions do in the SQL world – gets a substring from a string.
4 Ways to Return a Key’s Expiry in Redis
There are several ways to return a key’s expiry in Redis. The method used depends on how we want the expiry to be returned.
We can use the TTL command to return the timeout in seconds. We can alternatively use the PTTL command to return it in milliseconds. Another way to do it is to use the EXPIRETIME which returns the absolute Unix timestamp of the key in seconds, or the PEXPIRETIME command which returns the absolute Unix timestamp of the key in milliseconds.
How to Increment a Floating Point Number in Redis
The INCR command is commonly used in Redis to increment a value by one. And the INCRBY command can be used to increment a valued by a specified integer. But neither of those commands let us work with floating point numbers.
If we want to use floating point numbers, we can use the INCRBYFLOAT command.
Subtract Hours from a Time Value in SQLite
In SQLite, we can use the TIME() function to subtract one or more hours from a time value.
For datetime values, we can use the DATETIME() function.
3 Ways to Get the Start of the Month in MariaDB
Here are three options for returning the first day of a month in MariaDB.
This could be the first day of the current month, or the first day of the month based on a date that we specify.
Return Only Numeric Values in SQL
If you ever need to use SQL to return just the numeric values in a character column, the method you use will largely depend on your DBMS. Most DBMSs support regular expressions (regex), but some don’t. And some include functions that can detect numeric values.
Here are examples of how to do it in the more popular DBMSs.