1.6 Selecting Rows

Question 1

operator / operands

Answer 1

An operator is a symbol that computes a value from one or more other values, called operands: Arithmetic operators compute numeric values from numeric operands. Comparison operators compute logical values TRUE or FALSE. Operands may be numeric, character, and other data types. Logical operators compute logical values from logical operands.

Question 2

unary operator

Answer 2

A unary operator has one operand.
ex: logical operator NOT

Question 3

binary operator

Answer 3

A binary operator has two operands.

Question 4

expression

Answer 4

An expression is a string of operators, operands, and parentheses that evaluates to a single value. Operands may be column names or fixed values. The value of an expression may be any data type.

Question 5

operator precedence

Answer 5

Operators in an expression are evaluated in the order of operator precedence, shown in the table below. Operators of the same precedence are evaluated from left to right. Regardless of operator precedence, expressions enclosed in parentheses are evaluated before any operators outside the parentheses are applied.

Question 6

SELECT / FROM

Answer 6

The SELECT statement selects rows from a table. The statement has a SELECT clause and a FROM clause. The FROM clause specifies the table from which rows are selected. The SELECT clause specifies one or more expressions, separated by commas, that determine what values are returned for each row.

Question 7

result table

Answer 7

The SELECT statement returns a set of rows, called the result table.

Question 8

LIMIT

Answer 8

MySQL has a LIMIT clause that limits the number of rows returned by a SELECT statement.

Question 9

condition

Answer 9

A condition is an expression that evaluates to a logical value.

Question 10

WHERE

Answer 10

A SELECT statement has an optional WHERE clause that specifies a condition for selecting rows. A row is selected when the condition is TRUE for the row values. A row is omitted when the condition is either FALSE or NULL.

Question 11

Arithmetic operators

Answer 11

+ - * / % ^
compute numeric values from numeric operands.

Question 12

Comparison operators

Answer 12

= != <> < <= > >=
compute logical values and returns TRUE or FALSE.

Question 13

Logical operators

Answer 13

AND OR NOT
compute logical values from logical operands.