The LIKE operator is another extremely powerful
tool to help you define your search. In its most simple form, the LIKE
operator functions just like the "=" operator. That is, it matches
for equality in the WHERE clause. Thus, if we were to search our
EMPLOYEES table, the statement:
SELECT EMP_NAME, EMP_NUM
FROM EMPLOYEES
WHERE EMP_NAME = 'Lim Sing Yuen';
would be the same as saying:
SELECT EMP_NAME, EMP_NUM
FROM EMPLOYEES
WHERE EMP_NAME LIKE 'Lim Sing Yuen';
In either case, you would get:
EMP_NAME EMP_NUM
-------------------------------
Lim Sing Yuen 002
-------------------------------
However, the real umph of the LIKE operator comes
from its ability to incorporate wildcards. Specifically, the
LIKE operator can be used with the "%" and the "_" operator. The
"%" operator can be used to match any string of any length and the "_"
operator is used to match any single character. But this is best
seen by example. Consider the following
SELECT EMP_NAME, EMP_NUM
FROM EMPLOYEES
WHERE EMP_NAME LIKE 'Lim%';
In this case, you would get the following:
EMP_NAME EMP_NUM
-------------------------------
Lim Li Chuen 001
Lim Sing Yuen 002
-------------------------------
Notice that in both cases, the search
string begins with "Lim". The "%" wildcard specifies that
so long as the string includes the string "Lim", it
matches
Consider the "_" operator.
SELECT EMP_NAME, EMP_NUM
FROM EMPLOYEES
WHERE EMP_NUM LIKE '00_';
In this case, you would get all the
records returned that included a "00" followed by any
other character:
EMP_NAME EMP_NUM
-------------------------------
Lim Li Chuen 001
Lim Sing Yuen 002
Loo Soon Keat 003
-------------------------------
