In Redis, the MGET command allows us to get the values of multiple keys at once. The values are returned in an array reply.
If a specified key doesn’t exist, MGET returns nil for that key.
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Redis MSET Command Explained
In Redis, the MSET command allows us to set multiple keys at once. It replaces any existing values, just as SET does.
SQL Server CASE Statement
The SQL Server CASE statement evaluates a list of conditions and returns one of multiple possible result expressions.
Although it’s commonly known as the “CASE statement”, the SQL Server documentation lists it as an expression. Plus it’s referred to as the “CASE expression” in the SQL standard. Some other DBMSs distinguish between the CASE statement and the CASE expression. Either way, here’s a quick rundown on how the “CASE statement” (or CASE expression) works in SQL Server.
Redis SET Command Explained
In Redis, the SET command sets a key to hold a given string value.
If the key already holds a value, it is overwritten with the new value. Also, any previous time to live associated with the key is discarded (assuming a successful SET operation).
Redis GET Command Explained
In Redis, the GET command returns the value of a given key. If the key doesn’t exist, it returns nil.
An error is returned if the value stored at key is not a string.
Redis LASTSAVE Command Explained
When using Redis, we can use the LASTSAVE command to get the Unix time of the last DB save.
More specifically, LASTSAVE returns the Unix time of the last DB save executed with success.
SQL NVL2() Explained
Some DBMSs have an NVL2() function that 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 exactly three arguments. This allows us to specify a different value to return in the event the first argument is not null.
In contrast, with the NVL() function, some DBMSs accept only two arguments (which makes the function a synonym for the IFNULL() function) while others accept an unlimited number of arguments (which makes it a synonym for the COALESCE() function).
SQL NVL() Explained
Some DBMSs provide an NVL() function, which can be used when working with potentially NULL values. The function allows us to replace any NULL values with another value.
Oracle CASE Statement
In Oracle Database, the CASE statement compares a list of conditions and returns one of multiple possible expressions.
Oracle Database’s CASE statement is very similar to the CASE expression (which is defined in the SQL standard (ISO/IEC 9075)). However, Oracle supports both the CASE expression and the CASE statement, and there’s a distinction between the two. The CASE statement can be used to execute of a sequence of PL/SQL statements, whereas the CASE expression returns a single value. Also, there’s a difference in how they deal with the lack of an ELSE clause when a condition is not met.
Oracle CASE Expression
In Oracle Database, the CASE expression compares a list of conditions and returns one of multiple possible expressions. It allows us to use IF … THEN … ELSE logic in SQL statements without having to invoke procedures.
The CASE expression is included in the SQL standard (ISO/IEC 9075), and most major RDBMSs support it.
Oracle also has a CASE statement that’s very similar to the CASE expression, but with some minor differences.