# PL/SQL关系运算符

`=`检查两个操作数的值是否相等，如果是，则条件成立。(A = B)为假
`!=`,`<>``~=`检查两个操作数的值是否相等，如果两个值不相等则条件成为真。(A != B)为真
`>`检查左操作数的值是否大于右操作数的值，如果是，则条件成为真。(A > B) 为假
`<`检查左操作数的值是否小于右操作数的值，如果是，则条件成为真。(A < B) 条件为真。
`>=`检查左操作数的值是否大于或等于右操作数的值，如果是，则条件成为真。(A >= B) 为假
`<=`检查左操作数的值是否小于或等于右操作数的值，如果是，则条件成为真。(A <= B) 为真

``````DECLARE
a number (2) := 21;
b number (2) := 10;
BEGIN
IF (a = b) then
dbms_output.put_line('Line 1 - a is equal to b');
ELSE
dbms_output.put_line('Line 1 - a is not equal to b');
END IF;
IF (a < b) then
dbms_output.put_line('Line 2 - a is less than b');
ELSE
dbms_output.put_line('Line 2 - a is not less than b');
END IF;

IF ( a > b ) THEN
dbms_output.put_line('Line 3 - a is greater than b');
ELSE
dbms_output.put_line('Line 3 - a is not greater than b');
END IF;
-- Lets change value of a and b
a := 5;
b := 20;
IF ( a <= b ) THEN
dbms_output.put_line('Line 4 - a is either equal or less than b');
END IF;
IF ( b >= a ) THEN
dbms_output.put_line('Line 5 - b is either equal or greater than a');
END IF;
IF ( a <> b ) THEN
dbms_output.put_line('Line 6 - a is not equal to b');
ELSE
dbms_output.put_line('Line 6 - a is equal to b');
END IF;
END;
/
``````

``````Line 1 - a is not equal to b
Line 2 - a is not less than b
Line 3 - a is greater than b
Line 4 - a is either equal or less than b
Line 5 - b is either equal or greater than a
Line 6 - a is not equal to b

PL/SQL procedure successfully completed
``````

原文作者：PL/SQL教程
原文地址: https://www.yiibai.com/plsql/plsql_relational_operators.html
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