What are the main data types used in the fields of relational databases?

In relational databases, the main data types for table fields include:

• Numeric types: INT, SMALLINT, BIGINT, DECIMAL, NUMERIC, FLOAT, DOUBLE
• String types: CHAR, VARCHAR, TEXT
• Date and time: DATE, TIME, DATETIME, TIMESTAMP
• Boolean: BOOLEAN (or BIT in some DBMS)
• Binary data: BLOB, BINARY

Each type is chosen depending on the nature of the data and the requirements for storage and performance. For example, INT is used for storing integers, VARCHAR with length restrictions for text, and DATE or TIMESTAMP for dates.