For example, even a simple task like concatenating two database
fields needs to be written like this (for databases conforming to the
SQL-92 standard):
SELECT first_name || ' ' || last_name FROM table
Other databases require one of these forms:
SELECT first_name + ' ' + last_name FROM table
SELECT CONCAT(first_name, ' ', last_name) FROM table
SELECT CONCAT(CONCAT(first_name, ' ') last_name) FROM table
SELECT first_name CONCAT ' ' CONCAT last_name FROM table
The SQL dialect used by different database systems is riddled with
such inconsistencies, not to mention endless "extensions"
to the standard. This is a major headache for developers wishing to
write an application that will work with any of a number of
databases.