In SQLite, the CASE expression compares a list of conditions and returns one of multiple possible expressions.
The CASE expression is included in the SQL standard (ISO/IEC 9075), and most major RDBMSs support it.
Author: Ian
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.
Continue readingRedis LTRIM Command Explained
In Redis, the LTRIM command allows us to trim a list to a specified number of elements. We specify the starting and ending index, which is used to trim the list to just that range.
Get the First, Second, Third, or Fourth Monday of a Year in SQLite
We can use SQLite’s DATE() function to return the first, second, third, fourth, etc instance of a given day within a given year.
We can use the same technique to return the first Monday of each month in the year.
It’s not limited to Monday though. The same techniques can be used on Tuesday, Wednesday, Thursday, Friday, etc.
Continue readingRedis LSET Command Explained
In Redis, the LSET command allows us to set a list element to a different value, based on its index.
Redis LREM Command Explained
In Redis, we can use the LREM command to remove one or more elements from a list. The number of elements removed depends on the arguments we pass.
Redis LINSERT Command Explained
In Redis, the LINSERT command allows us to insert an element into a list.
We have the choice of inserting it either before or after a specified element.
Continue readingSet an Expiry on an Existing Redis Key Only When the Key Doesn’t Already Have an Expiry
When setting an expiry for an existing key in Redis, we now have the option to set the expiry only if the key doesn’t already have an expiry. That’s because Redis 7.0.0 introduced some new options that allows us to do this and other things.
In this case, we can use the NX option when setting the expiry to specify that the expiry should only be set if the key doesn’t already have an expiry. We can use this option on commands such as EXPIRE, EXPIREAT, PEXPIRE, and PEXPIREAT.
Redis LPOS Command Explained
In Redis, the LPOS command returns the index of matching elements inside a list.
Add Seconds to a Time Value in PostgreSQL
In PostgreSQL, we can use the + operator to add one or more seconds to a time value.
By “time” value, this could be an actual time value, a timestamp, or an interval. We can also add seconds to a date value or a date and time combination.