What are string constants in sql

String constants in SQL are special values ​​used to represent text data. They are enclosed in single quotes (') or double quotes (") and can contain any characters. They have two types: single quotes String constants and double quotes String constants are widely used in condition specification, data provision, derived column creation and function parameters. Single quotes are usually used, but double quotes can contain single quote characters and span multiple lines.

What are string constants in SQL?

In SQL, string constants are special values ​​used to represent text data. They are usually enclosed in single quotes (') or double quotes ("). String constants can contain any characters, including letters, numbers, symbols, and spaces.

Types of string constants

There are two types of string constants in SQL:

• Single quoted string Constants: Enclosed in single quotes (').
• Double-quoted string constants: Enclosed in double quotes (").

Use of string constants

String constants have a wide range of uses in SQL, including:

• Specifying conditions in the WHERE clause (for example, WHERE name = 'John')
• In INSERT and provide data in the UPDATE statement (for example, INSERT INTO users (name) VALUES ('John'))
• Create derived columns in the SELECT statement (for example, SELECT name || ' ' || surname AS full_name)
• As a parameter in a function (for example, UPPER('john'))

Select single or double quotes

Usually used Single-quoted string constants, as they are more common in SQL. However, there are some advantages to using double-quoted string constants:

• They can contain single-quote characters without escaping (for example, " John's car")
• They can span multiple lines (for example, "This is a very long string that spans multiple lines.")

Example

The following are some examples of SQL string constants:

• 'John Doe'
• "Mary Johnson"
• 'This is a string constant with a single quote: '''
• "This is a string constant with a double quote: ""

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