Less01 Retrieving Data Using the SQL SELECT Statement

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Basic SELECT Statement

Selecting All Columns

Selecting Specific Columns

Using Arithmetic Operators

Operator Precedence

Defining a Null Value

 A null is a value that is unavailable, unassigned, unknown, or inapplicable.

 A null is not the same as a zero or a blank space.

Null Values
in Arithmetic Expressions

Arithmetic expressions containing a null value evaluate to null.

Using Column Aliases

Concatenation Operator

A concatenation operator:

Links columns or character strings to other columns

Is represented by two vertical bars (||)

Creates a resultant column that is a character expression

Using Literal Character Strings

Alternative Quote (q) Operator

Specify your own quotation mark delimiter

Choose any delimiter

Increase readability and usability

Duplicate Rows

The default display of queries is all rows, including duplicate rows.

Displaying Table Structure