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Mastering Advanced SQL Techniques with MySQL

Introduction to SQL Statements

Explore how to construct SQL statements including data definition, manipulation, and transactional commands. Understand the role of user-defined variables, prepared statements, and transaction control to manage data efficiently and ensure database integrity.

We'll cover the following...

The basic building block of SQL is a statement. Chaining multiple statements with the ; delimiter we arrive at a complete SQL script. To that extent, consider the following SQL code:

MySQL
-- Remove any previous definition of `date_and_time`.
DROP TABLE IF EXISTS date_and_time;
-- Generate a temporary table for the showcase of temporal data types.
CREATE TEMPORARY TABLE date_and_time
(
    date      DATE      DEFAULT (CURRENT_DATE),
    time      TIME      DEFAULT (CURRENT_TIME),
    datetime  DATETIME  DEFAULT NOW(),
    timestamp TIMESTAMP DEFAULT NOW(),
    year      YEAR      DEFAULT (CURRENT_DATE)
);
-- Record an empty row of temporal data types.
INSERT INTO date_and_time VALUE ();

This SQL script contains three statements:

  • Ensuring any existing table named date_and_time is dropped from the database to prevent errors from attempting to create a table that already exists. It's a way to start fresh with the upcoming table definition (line 2).

  • Defining the creation of a temporary table named date_and_time. This table is meant to showcase various temporal data types in SQL. Each column is designed to store a different kind of temporal data (lines 5–12)

  • Inserting a new row into the date_and_time table without specifying any values (VALUE ()). Due to the default values defined in the table schema, ...