PostgreSQL – CHAR Data Type
In PostgreSQL, the char data type, also known as the fixed-length character string type, is used to store strings of fixed length. It’s important to note that the char type is not the same as the variable-length character string type (varchar). Here are some key points about the char data type:
- Fixed Length: The
chardata type stores strings of a specific length that you define when creating the column. Any string stored in acharcolumn will be padded with spaces to match the defined length. - Padding: If the stored string is shorter than the defined length, PostgreSQL adds trailing spaces to pad it to the specified length. If the string is longer, PostgreSQL will truncate it.
- Size: The storage size for a
charcolumn is fixed and depends on the defined length. For example, achar(10)column will always take up 10 bytes of storage. - Comparison and Trimming: When comparing
charvalues, PostgreSQL considers trailing spaces. If you want to perform a comparison without considering the padding, you might need to use functions likeTRIM().
Here’s an example of using the char data type:
CREATE TABLE product_codes(product_id serial PRIMARY KEY,product_code char(6));
INSERT INTO product_codes (product_code)VALUES ('ABC123');
SELECT * FROM product_codesWHERE product_code = 'ABC123';
In this example, a product_code column of type char is used to store product codes. The char data type is suitable when you want to enforce a fixed length for strings, but be cautious about padding and trimming when comparing values.