How to select a different database in Redis?
Jul 05, 2025 am 12:16 AM
To switch databases in Redis, use the SELECT command followed by the numeric index. Redis supports multiple logical databases (default 16), and each client connection maintains its own selected database. 1. Use SELECT index (e.g., SELECT 2) to switch to another database. 2. Verify with commands like KEYS * or DBSIZE. 3. Ensure the index is within configured limits. 4. Note that databases are unnamed and identified only by numbers. 5. Loop through indices with DBSIZE to infer used databases. 6. Consider prefixing keys instead of using separate databases in clusters or distributed setups where SELECT may not be supported.
To switch to a different database in Redis, you use numeric indexes — Redis supports multiple logical databases (defaulting to 16), and switching between them is as simple as using the SELECT command followed by the index number.
Here’s how it works in practice.
How to Use the SELECT Command
The main way to change databases is by running:
SELECT index
Where index is a number representing the database you want to switch to. For example:
SELECT 2
This will move your current connection to database 2. You can verify this by running commands like KEYS * to see what keys exist there.
Keep in mind that:
- The index must be less than the total number of databases configured in Redis (usually 16 by default).
- Each client connection maintains its own selected database.
- There's no way to name databases — they’re only identified by numbers.
Checking What Databases Exist
Redis doesn’t provide a built-in command to list all available databases, but you can infer which ones are used by checking for keys across indexes. One approach is to loop through possible indices and run DBSIZE:
SELECT 0 DBSIZE SELECT 1 DBSIZE
This lets you see how many keys are in each database. If you're managing Redis manually, keeping track of which data goes into which index helps avoid confusion later.
Using Redis Databases Effectively
Since Redis databases are isolated from each other, they’re useful for separating different types of data or environments (e.g., dev, staging, production). However, some things to note:
- Not all Redis clients support multiple databases equally — check your client library.
- Some hosting platforms may restrict or ignore database selection.
- It's easy to forget which database you're on, especially during debugging.
A common workaround is to prefix keys instead of relying on separate databases, especially when working in distributed setups or with Redis clusters where SELECT isn't supported.
Switching databases in Redis is straightforward, but also limited in flexibility.
Basically, just use SELECT followed by the right index — not complicated, but something to handle carefully depending on your setup.
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