Database.Guide – Page 148

PostgreSQL DATE_BIN() Function Explained

November 24, 2022 by Ian

In PostgreSQL, the DATE_BIN() function enables us to “bin” a timestamp into a given interval aligned with a specific origin. In other words, we can use this function to map (or force) a timestamp to the nearest specified interval.

This can be handy when we want to truncate a timestamp to a given interval, for example a 10 minute interval. We can specify the interval (e.g. 10 minutes, 15 minutes, 30 minutes, etc), and we can specify the starting point for the interval. Therefore, we can have the interval starting at any odd time we want (it doesn’t need to start on the hour or anything like that).

3 Ways to Update a Field in a Redis Hash

November 23, 2022 by Ian

The following commands can be used to update a field in a Redis hash. The command we use will depend on the type of data that’s stored in the field.

How to Return Field Values when using HRANDFIELD in Redis

November 22, 2022 by Ian

In Redis, we can use the HRANDFIELD command to return random fields from a given hash. By default, only the field names are returned.

But what if we want to include the field values?

In this case, we can use the WITHVALUES option when calling the command.

4 Ways to Clone a Table in MySQL

November 21, 2022 by Ian

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.

Fix: “ERR wrong number of arguments for ‘smove’ command” in Redis

November 20, 2022 by Ian

If 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.

How to Delete a Field in a Redis Hash

November 19, 2022 by Ian

If you’ve got a Redis hash with a field that needs to be deleted, you can use the HDEL command.

Fix “ERR syntax error” when calling SRANDMEMBER in Redis

November 18, 2022 by Ian

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.