Data Literals

MySQL Tutorials - Herong's Tutorial Examples

∟Data Literals

Describes how to enter data into programs as data literals for different datatypes.

Now we know the types of data, and how they are stored in memory. Next we need know how data can get in to the computer. One way is to enter it through the program source code as a data literal.

Data Literal: An program source element that represents a data value. Data literals can be divided into multiple groups depending the type of the data it is representing and how it is representing.

1. Character String Literals are used to construct character strings, exact numbers, approximate numbers and data and time values. The syntax rules of character string literals are pretty simple:

A character string literal is a sequence of characters enclosed by quote characters.
The quote character is the single quote character "'".
If "'" is part of the sequence, it needs to be doubled it as "''".

Examples of character string literals:

'Hello world!'
'Loews L''Enfant Plaza'
'123'
'0.123e-1'
'1999-01-01'

2. Hex String Literals are used to construct character strings and exact numbers. The syntax rules for hex string literals are also very simple:

A hex string literal is a sequence of hex digits enclosed by quote characters and prefixed with "x".
The quote character is the single quote character "'".

Examples of hex string literals:

x'41424344'
x'31323334'
x'31323334'
x'01'
x'0001'
x'ff'
x'ffffffff'
x'ffffffffffffffff'

3. Numeric Literals are used to construct exact numbers and approximate numbers. Syntax rules of numeric literals are:

A numeric literal can be written in signed integer form, signed real numbers without exponents, or real numbers with exponents.

Examples of numeric literals:

1
-22
33.3
-44.44
55.555e5
-666.666e-6

4. Date and Time Literals are used to construct date and time values. The syntax of date and time literals are:

A date literal is written in the form of "DATE 'yyyy-mm-dd'".
A time literal is written in the form of "TIMESTAMP 'yyyy-mm-dd hh:mm:ss'".

Examples of data and time literals:

DATE '1999-01-01'
TIMESTAMP '1999-01-01 01:02:03'

5. Time Interval Literals are used to construct time intervals with different time units.

A time interval literal is written in the form of "INTERVAL 'n' unit", where unit can be YEAR, MONTH, DAY, HOUR, MINUTE, or SECOND.

Examples of time interval literals:

INTERVAL '3' YEAR
INTERVAL '1' DAY
INTERVAL '4' MONTH
INTERVAL '1' HOUR
INTERVAL '5' MINUTE
INTERVAL '9' SECOND

6. Null Literal is used to construct a null value for any data type. The syntax of null literal is the word "null".

Table of Contents

About This Book

Introduction of SQL

MySQL Introduction and Installation

Introduction of MySQL Programs

PHP Programs and MySQL Server

Perl Programs and MySQL Servers

Java Programs and MySQL Servers

►Datatypes and Data Literals

Introduction of Datatype

Data Binary Representations

►Data Literals

Data Literal Evaluation

Character String Literal Evaluation Examples

Hex String Literal Evaluation Examples

Numeric Literal Evaluation Examples

Operations and Expressions

Character Strings and Bit Strings

Commonly Used Functions

Table Column Types for Different Types of Values

Using DDL to Create Tables and Indexes

Using DML to Insert, Update and Delete Records

Using SELECT to Query Database

Window Functions for Statistical Analysis

Use Index for Better Performance

Transaction Management and Isolation Levels

Locks Used in MySQL

Defining and Calling Stored Procedures

Variables, Loops and Cursors Used in Stored Procedures

System, User-Defined and Stored Procedure Variables

MySQL Server Administration

Storage Engines in MySQL Server

InnoDB Storage Engine - Primary and Secondary Indexes

Performance Tuning and Optimization

Bulk Changes on Large Tables

MySQL Server on macOS

Installing MySQL Server on Linux

Connection, Performance and Second Instance on Linux

Archived Tutorials

References

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