SQL Tables Content.

What is a Database Table?

• Tables are the basic building blocks in any database.
• They hold the rows and columns of your data.
• You can create tables, change them, and remove them.
• Normally, a user who creates a table is owner of the table and is responsible for granting permission to use it. That means how to give permission to use what and how.
• When you create a table with SQL, you do at least the following:
  • Name of the table.
  • Name of the columns it contains.
  • Specify the data type of each column.
  • Specify the null status of each column - whether that column permits or forbids null values.
• Almost all vendors have accepted additional possibilities for the CREATE TABLE statement which is supported in SQL-standard, including:
  • Defaults (values assumed when you don't explicitly enter anything, such as today's date, on a sales order).
  • Constraints that check (limit) the possible values you can enter for a column (for example, pub_ids can be 0736, 0877, or 1389 only).
  • Constraints that defines a column as primary key, unique, or both.
  • Constraints that defines index for columns to achieve fast search and data retrieval.
  • Constraints that can set up reference checks among primary and foreign keys.