1. Steps to design database: (1). Requirements analysis stage (2). Summary design stage: draw ER model diagram (3). Detailed design stage: convert ER model diagram into database table (4). Code writing stage (5 ). Testing phase (6). Deployment and installation 2. Outline design phase: (1). Collect information (2). Identify objects (3). Identify the detailed information that needs to be stored for each object (4). Identify the relationships between objects Relationships such as: the first step is usually to read the requirements analysis document, then the second step is to find the entity, the third step is to set the attributes of the corresponding entity class, and finally to set the relationship between each entity (such as primary and foreign key relationships or one-to-many-to-many One-to-many-to-many relationship) 3. Draw ER diagram (1). Entity (2). Attribute (3). Relationship (4). Mapping cardinality (5). Entity relationship diagram rectangle represents entity set ellipse represents attribute diamond represents Relationship set straight lines are used to connect attributes and entity sets, and are also used to connect entity sets. Relationship set straight lines can have directions (arrows) to represent the mapping base of the relationship set: 1:1, 1:N, M:N 4. Three major Paradigm: first normal form: ensure the atomicity of each column; second normal form: based on the first normal form, whether there is a partially dependent relationship (for composite primary keys) and whether it only describes one thing; third normal form: in the second normal form On the basis of , there is no transitive dependency relationship.