In SQL Server, the IIF() function (not to be confused with the IF statement) is a conditional function that returns the second or third argument based on the evaluation of the first argument.
It’s a shorthand way for writing a CASE expression. It’s logically equivalent to CASE WHEN X THEN Y ELSE Z END assuming IIF(X, Y, Z).
IIF() is an abbreviation for Immediate IF.
Most (probably all) programming languages include some form of the IF statement that allows programmers to write conditional code. That is, code that will execute only if a certain condition is true.
It’s a very simple concept. Basically it goes like this:
“If this, do that.”
Most languages simply call it IF, but some have their own twist on the name (for example, in ColdFusion/CFML, it’s called CFIF).
In any case, they essentially do the same thing.
In SQL Server (or more precisely, its programming language T-SQL) it’s called IF.
In PostgreSQL, you can use the AT TIME ZONE clause to convert a timestamp to another timezone.
In PostgreSQL, the make_interval() function creates an interval from years, months, weeks, days, hours, minutes and seconds fields.
You provide the years, months, weeks, days, hours, minutes and/or seconds fields, and it will return an interval in the interval data type.
In PostgreSQL, the make_timestamptz() function allows you to create a timestamp with time zone from its year, month, day, hour, minute and seconds fields, as well as an optional timezone field.
In PostgreSQL, the make_date() function allows you to create a date from its separate year, month and day fields.
Each date part is provided as an integer, and the result is returned as a date.
In PostgreSQL, the make_time() function allows you to create a time from its hour, minute and seconds fields.
In PostgreSQL, the make_timestamp() function allows you to create a timestamp from its year, month, day, hour, minute and seconds fields.
In PostgreSQL, the statement_timestamp() function returns the current date and time (including the time zone offset), at the start of the current statement.
The function doesn’t accept any parameters, so you can’t specify its precision.
Also, statement_timestamp() is a non-SQL-standard function.
In PostgreSQL, the transaction_timestamp() function returns the current date and time (including the time zone offset), at the start of the current transaction.
It’s the equivalent of the traditional Postgres function now().
It’s also similar to the current_timestamp function (when called without an argument), except that it’s named to clearly reflect what it does.
The transaction_timestamp() function doesn’t accept any parameters, so you can’t specify its precision, whereas current_timestamp can be called with or without a precision parameter.
Also, transaction_timestamp() is a non-SQL-standard function.