The Redis HGET command allows us to get a value from a hash. It returns the value associated with the specified field in the hash at the specified key.
DBMS
Database Management Systems
3 Ways to Check if a Table has a Generated Column in SQLite
If you’re not sure if a table has a generated column in SQLite, you can quickly find out with either the .schema command, or by querying the sqlite_schema table.
Redis HRANDFIELD Command
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.
Redis HEXISTS Command
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.
Fix “ERR numkeys should be greater than 0” when using the SINTERCARD Command in Redis
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.
Redis HKEYS Command
The Redis HKEYS command returns all fields in the hash stored at the specified key.
Redis HDEL Command
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.
Redis HSETNX Command
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).
Redis HSET Command
In 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.
7 Ways to Insert Multiple Rows in SQL
We 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.