Tables

What is a Table?

Tables are the core unit of database schema. Tables are defined by a set of columns. Columns can be primary keys which act as a unique identifier for each row. Once a table schema is defined, rows containing data can be inserted into the table.

Table data is stored on disk. The way a database lays out it's table data on disk defines some of the performance characteristics of the database.

How to use Tables

Structure the data in your database into tables. Define relationships between tables using foreign key constraints. Use CREATE statements to create tables and ALTER statements to change their schema.

Difference between MySQL Table and Dolt Table

A MySQL and Dolt table function the same on the surface. CREATE and ALTER statements work the same on both.

Dolt and MySQL are row major, meaning row values are stored next to each other. However, MySQL stores data in a binary tree structure while Dolt stores table data on disk using a content-addressed binary tree called a prolly tree. This setup makes Dolt fairly comparable in query performance to MySQL while also providing history-independence and fast diff between versions. Fast diff powers Dolt's version control capabilities.

Interaction with Dolt Version Control

Dolt versions table schema and data. A table in Dolt is akin to a file in Git, it is the unit of change. Tables are the target of dolt add.

Example

mysql> show tables;
+----------------+
| Tables_in_docs |
+----------------+
| complex        |
| docs           |
+----------------+
mysql> alter table complex add column c4 blob;
mysql> show create table complex;
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table   | Create Table                                                                                                                                                                                                                                  |
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| complex | CREATE TABLE `complex` (
  `pk1` int NOT NULL,
  `pk2` varchar(47) NOT NULL,
  `c1` tinyint NOT NULL,
  `c2` datetime,
  `c3` json,
  `c4` blob,
  PRIMARY KEY (`pk1`,`pk2`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_bin |
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+