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.
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