Simple functions
The smallest element of a qualification is a function that tests the contents of a column against a specified value.
For example, in the following SELECT statement, the function
tests whether the value in the lname column is the character
string SMITH:
SELECT lname, fname, customer_num from customer
WHERE lname = "SMITH"In the preceding
example, the equal operator (=) represents the function equal() and
has two arguments, a column name and a string constant. The following
formats apply to simple qualification functions.
| Generic prototype | Description |
|---|---|
| function(column_name) | Evaluates the contents of the named column |
| function(column_name, constant) function(constant, column_name) | Evaluates the contents of the named column and the explicit value of the constant argument In a commuted argument list, the constant value precedes the column name. |
| function(column ?) | Evaluates the value in the specified column of the current row and a value, called a host variable, that a client program supplies |
| function(column, slv #) | Evaluates the value in the specified column of the current row and a value, called a statement-local variable (SLV), that the UDR supplies |
| function(column, constant, slv #) function(constant, column, slv #) | Evaluates the value in the specified column of the current row, an explicit constant argument, and an SLV |