Workshop closed - summary

Well done, @name! You leave the scriptorium as a true builder of shelves. Here is what you have learned:

What you have learned

• DDL is the language of defining structure: CREATE, ALTER, DROP.
• CREATE TABLE name (column TYPE constraints, ...); builds a new shelf.
• In a column definition we write the name first, then the type, and constraints at the end.

Data types - choosing the drawer

| Data | Type | |------|------| | whole numbers |

INT

| | amounts (with cents) |

DECIMAL(8,2)

| | short text |

VARCHAR(n)

| | long text |

TEXT

| | date |

DATE

| | date with time |

DATETIME

| | true/false |

BOOLEAN

| | list of options |

ENUM(...)

|

Constraints - rules of order

• PRIMARY KEY - unique identification of a row.
• AUTO_INCREMENT - automatic numbering.
• NOT NULL - a required field.
• DEFAULT - a default value.
• UNIQUE - uniqueness.

Rebuilding and removing

• ALTER TABLE ... ADD COLUMN ...

  - adds a column.

• ALTER TABLE ... MODIFY COLUMN ...

  - changes the type.

• ALTER TABLE ... DROP COLUMN ...

  - removes a column.

• ALTER TABLE ... RENAME TO ...

  - renames the table.

• DROP TABLE ...

  - removes the whole table (carefully!).

What's next?

You already have shelves. In the next location you will learn to place scrolls on them - that is, to insert, change and delete data with INSERT, UPDATE and DELETE. Onward, deeper into the Library!