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Explain Wildcard Operators in SQL??
We have already discussed about the SQL LIKE operator, which is used to compare a value to similar values using the wildcard operators.
SQL supports two wildcard operators in conjunction with the LIKE operator which are explained in detail in the following table.
| Sr.No. | Wildcard & Description |
|---|---|
| 1 | The percent sign (%) Matches one or more characters. Note − MS Access uses the asterisk (*) wildcard character instead of the percent sign (%) wildcard character. |
| 2 | The underscore (_) Matches one character. Note − MS Access uses a question mark (?) instead of the underscore (_) to match any one character. |
The percent sign represents zero, one or multiple characters. The underscore represents a single number or a character. These symbols can be used in combinations.
Syntax
The basic syntax of a '%' and a '_' operator is as follows.
SELECT FROM table_name WHERE column LIKE 'XXXX%' or SELECT FROM table_name WHERE column LIKE '%XXXX%' or SELECT FROM table_name WHERE column LIKE 'XXXX_' or SELECT FROM table_name WHERE column LIKE '_XXXX' or SELECT FROM table_name WHERE column LIKE '_XXXX_'
You can combine N number of conditions using the AND or the OR operators. Here, XXXX could be any numeric or string value.
Example
The following table has a number of examples showing the WHERE part having different LIKE clauses with '%' and '_' operators.
| Sr.No. | Statement & Description |
|---|---|
| 1 | WHERE SALARY LIKE '200%' Finds any values that start with 200. |
| 2 | WHERE SALARY LIKE '%200%' Finds any values that have 200 in any position. |
| 3 | WHERE SALARY LIKE '_00%' Finds any values that have 00 in the second and third positions. |
| 4 | WHERE SALARY LIKE '2_%_%' Finds any values that start with 2 and are at least 3 characters in length. |
| 5 | WHERE SALARY LIKE '%2' Finds any values that end with 2. |
| 6 | WHERE SALARY LIKE '_2%3' Finds any values that have a 2 in the second position and end with a 3. |
| 7 | WHERE SALARY LIKE '2___3' Finds any values in a five-digit number that start with 2 and end with 3. |
Let us take a real example, consider the CUSTOMERS table having the following records.
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 2 | Khilan | 25 | Delhi | 1500.00 | | 3 | kaushik | 23 | Kota | 2000.00 | | 4 | Chaitali | 25 | Mumbai | 6500.00 | | 5 | Hardik | 27 | Bhopal | 8500.00 | | 6 | Komal | 22 | MP | 4500.00 | | 7 | Muffy | 24 | Indore | 10000.00 | +----+----------+-----+-----------+----------+
The following code block is an example, which would display all the records from the CUSTOMERS table where the SALARY starts with 200.
SQL> SELECT * FROM CUSTOMERS WHERE SALARY LIKE '200%';
This would produce the following result.
+----+----------+-----+-----------+----------+ | ID | NAME | AGE | ADDRESS | SALARY | +----+----------+-----+-----------+----------+ | 1 | Ramesh | 32 | Ahmedabad | 2000.00 | | 3 | kaushik | 23 | Kota | 2000.00 | +----+----------+-----+-----------+----------+
