Adding a column to an existing table is a fundamental task in database management. It allows you to expand the information stored within a table. This operation is part of the Data Definition Language (DDL) in SQL. The syntax for adding a column is straightforward and involves specifying the column name, data type, and any constraints. Crucially, you must ensure the data type aligns with the expected data for that column. For instance, if you're adding a date of birth, you'd use a DATE or TIMESTAMP data type. Adding a column doesn't affect existing rows; it simply extends the structure to accommodate new data. This is different from updating existing rows, which modifies the data within the existing rows.