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 readingTag: how to
Fix “WRONGTYPE Operation against a key holding the wrong kind of value” when using SMEMBERS in Redis
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.
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.
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.
Continue reading5 Ways to Create a Table in SQL
Probably 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 reading7 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.
Continue readingFix “One or more scores can’t be converted into double” when using SORT or SORT_RO in Redis
If 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.
Add Minutes to a Time Value in SQLite
In SQLite, we can use the TIME() function to add a given number of minutes to a time value.
If we’re dealing with datetime values, we can use the DATETIME() function.
Fix: “ERR wrong number of arguments for ‘smembers’ command” in Redis
If you’re getting an error that reads “ERR wrong number of arguments for ‘smembers’ command” in Redis, it’s because you’re calling the SMEMBERS 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 one.
Continue readingHow to Rename a Key in Redis Without Fear of Overwriting any Existing Keys
If you need to rename a key in Redis, you may be wondering how to do it without overwriting any existing keys. If you use the RENAME command, and a key already exists with your new key name, you’ll overwrite the existing key.
Fortunately, Redis also has a RENAMENX command, which only renames the key if there’s no other key with the new name. So we can use this command whenever we need to rename a key without fear of overwriting any existing keys.