Posts Tagged with "databases"

Sometimes you might want to purge a set of similar Redis keys in one shot. So far, standard Redis "DEL" command does not allow to remove keys using patterns. However, there is a trick to do this action. Execute the following command in bash:

redis-cli -h [host] -p [port] KEYS "prefix:*" | xargs redis-cli DEL

Seems clear? Wait a minute! What if you use multiple databases (keyspaces) and need to remove keys from a database different from default (0) one? No problem there! Here is the solution:

For some programmers (especially for begginers) it might be a bit difficult to understand how do SQL joins work in real life. In fact, sometimes even experienced software developers are not able to explain what is the difference between JOIN, LEFT JOIN and RIGHT JOIN.

Luckily, I found, perhaps, one of the best visual representations of SQL joins I have ever seen which will definately help to understand the mechanism of SQL joins.

See more graphical diagrams and explanations here