When we have a table with a generated column, here are two methods we can use to return its definition.
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Database Management Systems
Redis INCRBY Command Explained
In Redis, the INCRBY command increments the value of a key by the specified amount.
If the key doesn’t exist, INCRBY creates the key with a value of 0 and then increments it by the specified amount.
An error occurs if the key contains a value of the wrong type or contains a string that cannot be represented as integer. INCRBY operations are limited to 64 bit signed integers.
Redis INCR Command Explained
In Redis, the INCR command increments the value of a specified key by one.
If the key doesn’t exist, INCR creates the key with a value of 0 and then increments it by one.
An error occurs if the key contains a value of the wrong type or contains a string that cannot be represented as integer.
Continue readingRedis PERSIST Command Explained
The Redis PERSIST command removes any existing timeout on a given key. It returns an integer reply of 1 if the timeout was removed, or 0 if the key doesn’t exist or doesn’t have an associated timeout.
Redis PTTL Command Explained
In Redis, the PTTL command returns the remaining time to live of a given key, in milliseconds.
If the key doesn’t have a timeout, an integer reply of -1 is returned. If the key doesn’t exist, -2 is returned.
PTTL works the same as the TTL command, except that it returns the result in milliseconds instead of seconds.
Redis TTL Command Explained
In Redis, the TTL command returns the remaining time to live of a given key, in seconds.
If the key doesn’t have a timeout, an integer reply of -1 is returned. If the key doesn’t exist, -2 is returned.
Redis also has a PTTL command, which works the same, but returns its result in milliseconds.
Redis PEXPIRETIME Command Explained
The Redis PEXPIRETIME command returns the absolute Unix timestamp in milliseconds at which the given key will expire. This is the number of milliseconds since 00:00:00 UTC on 1 January 1970 until the expiry time of the key.
This works exactly the same as EXPIRETIME, but it returns the Unix timestamp in milliseconds instead of seconds.
The PEXPIRETIME command was introduced in Redis 7.0.0.
Redis EXPIRETIME Command Explained
The Redis EXPIRETIME command returns the absolute Unix timestamp in seconds at which the given key will expire. This is the number of seconds since 00:00:00 UTC on 1 January 1970 until the expiry time of the key.
The EXPIRETIME command was introduced in Redis 7.0.0.
How to Create a Generated Column in Oracle
Oracle Database supports the creation of generated columns. A generated column is a column whose value is derived from an expression that computes values from other columns.
In Oracle Database, generated columns are usually referred to as virtual columns. Generated columns can also be referred to as computed columns in other RDBMSs (such as SQL Server). Either way, they do pretty much the same thing – they contain an expression that computes a value based on values in other columns in the same table.
Continue readingRedis EXPIREAT Command Explained
The Redis EXPIREAT command sets a timeout as a Unix timestamp on a given key. It works the same as the EXPIRE command, but with an absolute Unix timestamp instead of a time interval in seconds (which EXPIRE uses).