MySQL DDL - SQL

MySQL DDL - SQL refers to the Data Definition Language (DDL) statements used in MySQL to define and manipulate database objects. DDL statements are used to create, modify, and delete database objects such as tables, indexes, views, and stored procedures. As a programmer, it is essential to have an understanding of MySQL DDL - SQL to develop efficient and robust database applications.

Creating a table

To create a table in MySQL, we use the CREATE TABLE statement. The basic syntax for creating a table is as follows:

CREATE TABLE table_name (
    column1 datatype constraint,
    column2 datatype constraint,
    column3 datatype constraint,
    ...
    table_constraint
);

Here, table_name is the name of the table, column1, column2, column3, and so on are the names of the columns in the table, datatype is the data type of the column, and constraint specifies any constraints on the column. table_constraint is an optional constraint that can be added to the whole table.

Here is an example of creating a table called users with the columns id, name, email, and password:

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE,
    password VARCHAR(255) NOT NULL
);

In this example, we have added AUTO_INCREMENT to the id column, making it the primary key. We have also added NOT NULL to the name and password columns to ensure that they are not empty, and UNIQUE to the email column to ensure that no two users have the same email address.

Modifying a table

To modify a table, we use the ALTER TABLE statement. The basic syntax for altering a table is as follows:

ALTER TABLE table_name action;

Here, table_name is the name of the table, and action is the modification we want to make. There are several actions we can perform using the ALTER TABLE statement, such as adding a column, dropping a column, modifying a column, and so on.

Here is an example of adding a new column 'phone_number' in the 'users' table:

ALTER TABLE users ADD phone_number VARCHAR(20) AFTER email;

In this example, 'phone_number' column is added after the 'email' column.

Dropping a table

To delete a table from the database, we use the DROP TABLE statement. The basic syntax for dropping a table is as follows:

DROP TABLE table_name;

Here, table_name is the name of the table that we want to delete.

Conclusion

MySQL DDL - SQL is an essential part of MySQL that allows programmers to manipulate database objects. By understanding how to create, modify, and delete tables, we can develop efficient and robust database applications.