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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteA database is hard to maintain when rows lack dependable identity, relationships are left unenforced, or indexes are added without regard to how the application uses the data. A sound starting point is to model the information and relationships the application needs, then express important rules in the schema. The examples below use PostgreSQL 18 where behavior is product-specific; other database systems may differ.
Start with the information and relationships
Before creating tables, list the kinds of things the application needs to store and how they relate. For example, an online shop might represent customers, orders, and products. An order belongs to a customer, and an order can contain multiple products. Those facts help determine which entities need their own rows and where relationships belong.
PostgreSQL’s Data Definition documentation describes database structures and how they are defined. The specific modeling choices depend on what the application must represent; no single table layout suits every workload.
Give rows dependable identity
Use a primary key to identify each row. In PostgreSQL, a primary key must be unique and non-null, and declaring one automatically creates a unique B-tree index. That makes it a clear target for relationships and a reliable way to distinguish rows. See PostgreSQL 18’s Constraints documentation.
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A descriptive value—such as a person’s name or a product label—may change or be shared by multiple records. Use one as a key only when uniqueness and stability are genuine requirements of the data, rather than assumptions that happen to hold today.
Make relationships and validity rules explicit
A foreign key says that a value in one table must match an eligible row in another. In PostgreSQL, the referenced columns must be covered by a primary key, unique constraint, or qualifying unique index. This lets the database reject writes that would create a relationship to a missing row.
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Choose what should happen when a referenced row is updated or deleted. PostgreSQL supports configurable foreign-key actions; select one that matches the application’s meaning. For instance, deleting a parent record may be inappropriate if its dependent records must be retained, while other relationships may call for dependent rows to be removed. The correct action is a product and application design decision, not a universal default. Details are in the PostgreSQL 18 foreign-key documentation.
Use constraints for rules the database should enforce, such as required values, uniqueness, or permitted value conditions. A constraint prevents invalid writes only for the rule actually declared. Put rules that must hold across all clients at the database boundary rather than relying solely on each application path to remember them.
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Add indexes for the workload, not by reflex
Constraints and indexes serve related but distinct purposes. PostgreSQL automatically creates a unique B-tree index for a primary key, but it does not automatically index the columns that reference a foreign key. An index on those referencing columns may help when referenced rows are updated or deleted, or when queries search by the relationship. Whether it is worthwhile depends on the actual access and write patterns.
More indexes are not automatically better. Decide based on the queries the application runs, the changes it performs, and the maintenance burden an added index creates. The PostgreSQL documentation explains the foreign-key indexing behavior, but it does not establish a universal performance result for a particular schema or workload.
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Review a schema before relying on it
- Identity: Can every row be identified without relying on a value that may change or be duplicated?
- Relationships: Should a reference always point to an existing row? If so, is that rule declared as a foreign key?
- Validity: Which required, unique, or value-condition rules should the database reject when violated?
- Deletion and updates: Do the configured relationship actions match what the application should preserve or remove?
- Indexes: Which queries or relationship operations justify each index, and what write or maintenance cost does it add?
- Scope: Have product-specific behaviors been checked against the documentation for the database system and version actually in use?
For PostgreSQL 18, these checks align with the documented behavior of primary keys, foreign keys, and constraints. Other database systems may implement details differently, so verify their documentation before transferring a PostgreSQL-specific assumption.
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