Managing Constraints¶ Let us understand how we can manage constraints. We can add constraints while creating the tables or after creating the tables. Constraints such as NOT NULL, CHECK, FOREIGN KEY are automatically dropped when we drop the table. Even PRIMARY KEY and UNIQUE constraints are dropped if they are not used to enforce constraints. …
Different Types of Constraints¶ Let us understand details about different types of constraints used in RDBMS databases. Supported constraints: NOT NULL constraint CHECK constraint UNIQUE constraint PRIMARY KEY constraint FOREIGN KEY constraint All constraints can be added while creating the table or on pre-created tables using ALTER. Typically we define NOT NULL, CHECK constraints while …
Adding or Modifying Columns¶ Let us understand details about adding or modifying columns using ALTER TABLE command. New columns can be added to the existing table. However, if you want to add a column which cannot have null value then you need to follow these steps. Add column to the table. Update data in the …
Overview of Data Types¶ Let us get an overview of supported datatypes in Postgres. Here is the sample CREATE TABLE command for the review. CREATE TABLE users ( user_id SERIAL PRIMARY KEY, user_first_name VARCHAR(30) NOT NULL, user_last_name VARCHAR(30) NOT NULL, user_email_id VARCHAR(50) NOT NULL, user_email_validated BOOLEAN DEFAULT FALSE, user_password VARCHAR(200), user_role VARCHAR(1) NOT NULL DEFAULT …
DDL – Data Definition Language¶ Let us get an overview of DDL Statements which are typically used to create database objects such as tables. DDL Stands for Data Definition Language. We execute DDL statements less frequently as part of the application development process. Typically DDL Scripts are maintained separately than the code. Following are the …
Creating Tables and Indexes¶ Let us go through the details related to creating tables and indexes. We will also talk about how columns, constraints etc while going through the details related to tables and indexes. DDL – Data Definition Language Overview of Data Types Adding or Modifying Columns Different Types of Constraints Managing Constraints Indexes …
