Database Management Systems
Redis provides us with a convenient way to set multiple strings at once. Specifically, the MSET command enables us to set multiple strings in one go.
There’s also the MSETNX command which does the same thing, but only if none of the keys already exist.
Here are a couple of options for getting a list of tables in a database in PostgreSQL.
The first option is a psql command, the second involves querying an information schema view.
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.
Continue readingThe Redis TOUCH command alters the last access time of a key or keys. It allows us to alter the access time of a key without accessing it directly.
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.
In Redis, the EXISTS command checks whether the specified keys exist. It returns an integer reply with the number of keys that exist.
We can use the command to check for the existence of one key or multiple keys.
Continue readingThe Redis SORT_RO command is a read-only variant of the SORT command. It allows us to sort lists, sets, and sorted sets.
The SORT command enables us to have the sorted elements returned to the client, or stored in a separate key. But the SORT_RO command only allows us to have them returned to the client.
The SORT_RO variant was introduced in Redis 7.0.0 to enable SORT functionality in read-only replicas without breaking compatibility on command flags.
In Redis, the SORT command allows us to sort lists, sets, and sorted sets.
We can have the sorted elements returned to the client, or we can store them in a separate key.
Continue readingHere 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.
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