In PostgreSQL, the sign() function is used to indicate the sign of its argument.
It doesn’t simply return the actual sign. Rather, it returns -1 for negative numbers, 0 for zero, and 1 for positive numbers.
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How clock_timestamp() Works in PostgreSQL
In PostgreSQL, clock_timestamp() is a non-SQL-standard time function that returns the current date and time.
An important consideration of this function is that its result changes throughout the execution of a statement. Therefore, you could get a different result in different parts of the statement if you call the function multiple times within a single statement.
How cbrt() Works in PostgreSQL
In PostgreSQL, the cbrt() function returns the cube root of its argument.
The cube root of a number x is a number y such that y3 = x.
How sqrt() Works in PostgreSQL
In PostgreSQL, the sqrt() function returns the square root of its argument.
The square root of a number x is the number y such that y2 = x.
How Abs() Works in PostgreSQL
In PostgreSQL, the abs() function returns the absolute value of its argument.
The absolute value means how far the number is away from zero. Therefore, the absolute value of 7 is 7, and the absolute value of -7 is also 7.
Therefore, any negative values passed to abs() are returned as positive values. Positive values and zero are returned unchanged.
How pg_sleep() Works in PostgreSQL
In PostgreSQL, you can use the pg_sleep() function to delay execution for a given number of seconds.
It makes the current session’s process sleep until the specified number of seconds have elapsed. It works similar to MySQL‘s sleep() function, and also TSQL‘s waitfor statement in SQL Server.
The pg_sleep() function accepts a double precision argument, so you can also specify fractional-second delays.
The sleep delay will be at least as long as specified. However, it could be longer depending on factors such as server load, as well as your platform’s effective resolution of the sleep interval.
How pg_sleep_for() Works in PostgreSQL
In PostgreSQL, you can use the pg_sleep_for() function to delay execution for a given interval.
It makes the current session’s process sleep until the specified interval has elapsed.
The sleep delay will be at least as long as specified. However, it could be longer depending on factors such as server load, as well as your platform’s effective resolution of the sleep interval.
How pg_sleep_until() Works in PostgreSQL
In PostgreSQL, you can use the pg_sleep_until() function to delay execution until a specified timestamp.
This is useful for when a specific wake-up time is desired.
Note that pg_sleep_until is not guaranteed to wake up exactly at the specified time, but it will not wake up any earlier.
How Setseed() Works in PostgreSQL
In PostgreSQL, the setseed() function sets the seed for subsequent random() and random_normal() calls (value between -1.0 and 1.0, inclusive).
The random() function generates a pseudo-random number using a simple linear congruential algorithm. The random_normal() function generates a normally-distributed random number.
If setseed() is called, the results of subsequent random() and random_normal() calls in the current session are repeatable by re-issuing setseed() with the same argument.
How Random() Works in PostgreSQL
In PostgreSQL, the random() function returns a pseudo-random value in the range 0.0 <= x < 1.0.
It uses a simple linear congruential algorithm, which is one of the oldest and best-known pseudo-random number generator algorithms.
A pseudo-random number is a number that appears to be random, but is not truely random. A pseudo-random number is not truely random because its value was generated by a known seed. However, it will appear to be random if the user has no knowledge of the seed or algorithm that created it.
Therefore, pseudo-random numbers are often considered good enough for many applications.