SQL Wildcards – A Detailed Exploration

let’s aim to provide a comprehensive look at SQL wildcards across various types of databases.

Before diving in, it’s essential to have a handy reference point. Here’s a table that outlines the different types of wildcards available across SQL Server, MySQL, Oracle, and MS Access.

Each wildcard character or set of characters has a unique role to play in SQL. They can significantly simplify complex searches and make your database operations more efficient.

Let’s assume you have the following ‘Customers’ table to illustrate the use of these wildcards

| ID | Name      | Phone      |
|----|-----------|------------|
| 1  | Alice     | 1234567890 |
| 2  | Bob       | 2345678901 |
| 3  | Charles   | 3456789012 |
| 4  | Deborah   | 4567890123 |
| 5  | Erik      | 5678901234 |
| 6  | Fiona     | 6789012345 |

Now, let’s see how to use these wildcards in your SQL queries.

1) The % and _ Wildcards (SQL Server, MySQL, Oracle, MS Access)

These are the most common wildcards, used to match a string of any characters ( % ) or a single character ( _ ).

For example, if you want to find all customers whose names start with ‘A’, your SQL query might look something like this

SELECT * FROM Customers
WHERE Name LIKE 'A%';

Result:

| ID | Name      | Phone      |
|----|-----------|------------|
| 1  | Alice     | 1234567890 |

2) The [ ], [^], and – Wildcards (SQL Server and MS Access)

These wildcards are used to define a character set or a range of characters.

For example, if you want to find any customers whose name starts with a letter from ‘A’ to ‘C’, you could use the following query

SELECT * FROM Customers
WHERE Name LIKE '[A-C]%';

Result:

| ID | Name      | Phone      |
|----|-----------|------------|
| 1  | Alice     | 1234567890 |
| 2  | Bob       | 2345678901 |
| 3  | Charles   | 3456789012 |

3) The *, ?, and # Wildcards (MS Access)

In MS Access, * and ? are similar to % and _ in SQL, and # is used to represent a single numeric character.

For instance, to find all customers whose phone number starts with ‘123’ followed by any digit, you would use:

SELECT * FROM Customers
WHERE Phone LIKE '123#*';

Result:

| ID | Name      | Phone      |
|----|-----------|------------|
| 1  | Alice     | 1234567890 |

4) The [!] Wildcard (MS Access)

This wildcard matches any character not in the character set.

For example, to find all customers whose names do not start with ‘A’, ‘B’, or ‘C’, you would use

SELECT * FROM Customers
WHERE Name LIKE '[!A-C]*';

Result:

| ID | Name      | Phone      |
|----|-----------|------------|
| 4  | Deborah   | 4567890123 |
| 5  | Erik      | 5678901234 |
| 6  | Fiona     | 6789012345 |

Conclusion:

As you can see, SQL wildcards are powerful tools when it comes to data manipulation and retrieval. However, always use them judiciously to avoid unnecessary full-table scans, which can slow down your search process significa