In Redis, the RPUSHX command inserts one or more values into the tail of the list at the specified key, but only if the key exists and it contains a list.
If the key doesn’t exist, no operation is performed. If the key exists but it doesn’t contain a list, an error is returned.
Continue readingIn Redis, the RPUSH command inserts one or more values into the tail of the list at the specified key.
If the key doesn’t exist, it is created as an empty list before performing the push operation. If the key already holds a value that is not a list, an error is returned.
Continue readingIn Redis, the LPUSHX command inserts one or more values into the head of the list at the specified key, but only if the key exists and it contains a list.
If the key doesn’t exist, no operation is performed. If the key exists but it doesn’t contain a list, an error is returned.
Continue readingIn Redis, the LPUSH command inserts one or more values into the head of the list at the specified key.
If the key doesn’t exist, it is created as an empty list before performing the push operation. If the key already holds a value that is not a list, an error is returned.
Continue readingIn PostgreSQL, the CASE expression compares a list of conditions and returns one of multiple possible result expressions.
The CASE expression is included in the SQL standard (ISO/IEC 9075), and most major RDBMSs support it.
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.
In Redis, the OBJECT ENCODING command returns the internal encoding for the Redis object stored at the specified key.
In Redis, the RANDOMKEY command returns a random key from the currently selected database.
In Redis, the KEYS command returns all keys in the database matching a given pattern.
The Redis DUMP command serialises the value stored at a specified key in a Redis-specific format and returns it to the user.
The serialisation format contains a 64-bit checksum that is used to make sure errors will be detected. The values are in the same format used by the RDB. Also, an RDB version is encoded inside the serialised value, so that different Redis versions with incompatible RDB formats will refuse to process the serialised value.
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