An ESQL nested statement is a statement that is contained within another statement.
Consider the following ESQL program fragment:
IF Size> 100.00 THEN SET X = 0; SET Y = 0; SET REVERSE = FALSE; ELSE SET X = 639; SET Y = 479; SET REVERSE = TRUE; END IF;
In this example, you can see a single IF statement containing the optional ELSE clause. Both the IF and ELSE portions contain three nested statements. Those within the IF clause are executed if the operator> (greater than) returns the value TRUE (that is, if Size has a value greater than 100.00); otherwise, those within the ELSE clause are processed.
Many statements can have expressions nested within them, but only a few can have statements nested within them. The key difference between an expression and a statement is that an expression calculates a value to be used, whereas a statement performs an action (usually changing the state of the program) but does not produce a value.