Relationships between data tables

Relationship

???? Entity: is the real thing (physical or virtual), the computer is used to store information related to the entity.

???? Relationship: In reality, there is a certain relationship between entity and entity. In MySQL, the real-world relationship is divided into three kinds, a pair of one or one-to-many (many-to-one), many-to-many.

One

???? This table contains a lot of information (fields), but some fields are common, often used for queries, some fields, not frequently queried. If all are placed in a table, MySQL will be inefficient when it reads data.

Workaround:

???? Put commonly used information (the field of operation frequency) into one table, and information that is not frequently queried is placed in another table.

Such as:

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One-to-many

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More than the

Relationships between data tables