SQL SELECT statement is the most commonly used command. Our SQL basics tutorial teaches you (writing and using) that SQL SELECT statement is used to query or retrieve data from a table in the database. Get more on Portnov Computer School website - www.portnov.com
A query may retrieve information from specified columns or from all of the columns in the table. To create a simple SQL SELECT Statement, you must specify the column(s) name and the table name. The whole query is called SQL SELECT Statement.
The SQL SELECT statement returns a result set of records from one or more tables. A SELECT statement retrieves zero or more rows from one or more database tables or database views. In most applications, SELECT is the most commonly used Data Manipulation Language (DML) command. As SQL is a declarative programming language, SELECT queries specify a result set, but do not specify how to calculate it. The database translates the query into a "query plan" which may vary between executions, database versions and database software. This functionality is called the "query optimizer" as it is responsible for finding the best possible execution plan for the query, within applicable constraints.
Expressions combine many arithmetic operators, they can be used in SELECT, WHERE and ORDER BY Clauses of the SQL SELECT Statement.
Here we will explain how to use expressions in the SQL SELECT Statement. About using expressions in WHERE and ORDER BY clause, they will be explained in their respective sections.
The operators are evaluated in a specific order of precedence, when more than one arithmetic operator is used in an expression. The order of evaluation is: parentheses, division, multiplication, addition, and subtraction. The evaluation is performed from the left to the right of the expression.