Database Management Systems
MySQL provides us with several ways to copy a database table. The method we use will depend on our requirements.
We can choose to copy the table, its data, and its indexes. Or we can copy just the table and data without the indexes. We can alternatively generate the code that will enable us to copy the table later.
Continue readingIf you’re getting an error that reads “ERR wrong number of arguments for ‘smove’ command” in Redis, it’s because you’re calling the SMOVE command with the wrong number of arguments.
To fix this issue, make sure you’re passing the correct number of arguments. At the time of writing, the correct number of arguments for this command is three.
Continue readingIf you’ve got a Redis hash with a field that needs to be deleted, you can use the HDEL command.
If you’re getting an error that reads “ERR syntax error” when calling the SRANDMEMBER command in Redis, it could be that you’re passing too many arguments.
To fix this issue, be sure to pass the correct number of arguments. At the time of writing, SRANDMEMBER accepts up to two arguments. Any more than this results in an error.
I decided to compile a list of commands that can insert a new field into a Redis hash. Here are four options for inserting a new field into a Redis hash.
Continue readingThe Redis HINCRBYFLOAT command increments the field in the hash at the specified key by a floating point number. We specify how much we want the field to increment by when we call the command.
The Redis HINCRBY command increments the number that’s stored at the specified field in the hash at the specified key. We specify how much we want the field to increment by when we call the command.
The Redis HVALS command returns all values in the hash stored at the specified key.
The Redis HLEN command returns the number of fields in the hash stored at the specified key.
If you get an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when using the SMEMBERS command in Redis, it’s probably because you’re passing a key with the wrong data type to the command.
The SMEMBERS command is a “set” command, and so it is intended to be used on keys that contain a set. If the key holds a different data type, you’ll likely get the above error.