How do you perform case-insensitive searches in SQL?

Performing case-insensitive searches in SQL typically depends on the specific database management system (DBMS) you are using, as different DBMSs have different ways of handling case sensitivity.

Here are some common methods for performing case-insensitive searches in SQL:

1. 1.Using the UPPER() or LOWER() Function:
   One common approach is to convert both the search term and the column data to either uppercase or lowercase using the UPPER() or LOWER() function and then perform the comparison. This ensures that the case difference is ignored. Here's an example:

   SELECT * FROM table_name WHERE UPPER(column_name) = UPPER('search_term');
   

   or

   SELECT * FROM table_name WHERE LOWER(column_name) = LOWER('search_term');
   

   This method works with most relational database systems.

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3. 2.Using the ILIKE Operator (PostgreSQL): Some database systems, like PostgreSQL, provide a case-insensitive search operator called ILIKE. It works similarly to LIKE, but it's case-insensitive by default.

   SELECT * FROM table_name WHERE column_name ILIKE 'search_term';
   

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5. 3.Using COLLATE Clause (SQL Server and MySQL): SQL Server and MySQL allow you to use the COLLATE clause to specify a case-insensitive collation for a particular column in your query. For example:

   SELECT * FROM table_name WHERE column_name COLLATE Latin1_General_CI_AI = 'search_term';
   

   In this example, CI stands for case-insensitive, and AI stands for accent-insensitive (ignores diacritics).

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7. 4.Database Configuration (Change Collation): In some DBMSs, you can configure the collation for a database or a specific column to be case-insensitive by default. This setting affects all searches and comparisons in that database or column.

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9. 5.Using a Custom Function (Database-Specific): Some databases may offer custom functions or extensions for case-insensitive searching. These functions can vary widely between DBMSs.

It's important to note that the method you use for case-insensitive searching may vary depending on the database system you're working with. Be sure to consult your specific DBMS's documentation to understand the recommended approach for achieving case-insensitive searches in your environment.