# 第十四节 约束

- [14.1 NOT NULL 约束](/mysql/di-yi-zhang/index-13/not-null-yue-shu.md)
- [14.2 主键约束](/mysql/di-yi-zhang/index-13/zhu-jian-yue-shu.md)
- [14.2 外键约束](/mysql/di-yi-zhang/index-13/wai-jian-yue-shu.md)
- [14.4 UNIQUE 约束](/mysql/di-yi-zhang/index-13/unique-yue-shu.md)
- [14.5 CHECK 约束](/mysql/di-yi-zhang/index-13/check-yue-shu.md)