The Redis HRANDFIELD command allows us to get a random field from a given key.
The command accepts several arguments that allows us to specify the number of random fields returned, whether to include the same field multiple times, and whether or not to include the values with each field returned.
The HRANDFIELD command was introduced in Redis 6.2.0.
In Redis, the HEXISTS command allows us to check whether a field exists in a given hash. We pass the name of the key and the field to the command, and it returns 1 if the field exists, and 0 if it doesn’t.
If you’re getting an error that reads “ERR numkeys should be greater than 0” in Redis, it’s probably because you’re specifying a wrong value for the first argument when calling the SINTERCARD command.
To fix this issue, make sure you’re passing a valid non-zero value that matches the number of keys you’re comparing.
Continue readingThe Redis HKEYS command returns all fields in the hash stored at the specified key.
In Redis, the HDEL command enables us to delete one or more fields in a hash. It deletes the specified field/s at the specified key.
If the field doesn’t exist, it’s ignored. If the key doesn’t exist, it’s treated as an empty hash and 0 is returned.
In Redis, the HSETNX command enables us to set a field in a hash, but only if the field doesn’t already exist. It sets the field at the specified key to the value we provide.
If the key doesn’t exist, it’s created with the specified hash value. If the field already exists, nothing is set (i.e. the command has no effect).
Continue readingProbably the most common way of creating a table in SQL is to use a basic CREATE TABLE statement, along with the table’s definition. But that’s not the only way of doing it.
Below are five options for creating a table when using SQL.
Continue readingIn Redis, the HSET command enables us to set one or more fields in a hash. It sets the field/s at the specified key to the value/s we provide.
If the key doesn’t exist, it’s created with the specified hash value. If the field already exists, it is overwritten with the new value.
Continue readingWe can use the SQL INSERT statement to insert a row into a table. We can also use it to insert more than one row.
Below are seven ways to insert multiple rows into a table in SQL. Most of these examples should work in the major RDBMSs, with the possible exception of Oracle. But no worries, I’ve included an example just for Oracle.
Continue readingIf you’re getting an error that reads “One or more scores can’t be converted into double” when using either the SORT or SORT_RO commands in Redis, it could be because you omitted the ALPHA modifier when trying to sort string values.
If you want to sort string values lexicographically, you need to use the ALPHA modifier when using the SORT or SORT_RO command.