SQL tutorial
SQL - in simple words, it is a programming language for structured queries (SQL, Structured Query Language), which is used as an effective way to save data, find its parts, update, extract from...
Every self-respecting web developer should know SQL.Although it has existed since the 70s of last century, it is still very widely used, and without it it will be difficult to create...
Very many programmers look at SQL like a terrible beast. SQL - one of the few declarative languages, and its behavior is fundamentally different from how imperative, object-oriented and even...
SQL - in simple words, it is a programming language for structured queries (Structured Query Language), which is used as an effective way to save data, find its parts, update, extract from the...
SQL ALTER TABLE statement is used to add, modify or delete columns in a table. ALTER TABLE SQL statement is also used to rename a table. Add a column to a table SQL syntax of ALTER TABLE...
SQL UNION statement is used to combine the resulting sets of 2 or more SELECT operators. It removes repetitive strings between different SELECT requests.Each SELECT statement in UNION must...
SQL AVG function is used to return the average value of an expression in the SELECT operator. Syntax for AVG function in SQL SELECT AVG(aggregate_expression_id) FROM tabs [WHERE conds]Or...
SQL MAX function is used to return the maximum value of an expression in the SELECT operator. Syntax for MAX function in SQL SELECT MAX(aggregate_expression_id) FROM tabs [WHERE conds]Or...
SQL MIN function is used to return the minimum value of an expression in the SELECT operator. Syntax for MIN function in SQL SELECT MIN(aggregate_expression_id). FROM tabs [WHERE conds]Or...
SQL SUM function is used to return the sum of an expression in the SELECT operator. Syntax for SUM function in SQL SELECT SUM(aggregate_expression_id) FROM tabs [WHERE conds]Or syntax for...
Sql Count Function - COUNT is used to calculate the number of rows returned in the SELECT operator. Syntax for COUNT function in SQL SELECT COUNT(aggregate_expression_id) FROM tabs [WHERE...
SQL literals (strings, integers, decimal numbers and date and time values) are the same as a constant. We will consider several types of literals - string, integer, decimal and date and time...
SQL ALIASES (temporary names for columns or tables) with syntax and examples. SQL ALIASES can be used to create a temporary name for columns or tables.Column aliases are used to make it...
SQL provides a list of common SQL data types. These data types may not be supported by all relational databases. Data Types Syntax data type Explanation (if...
SQL comments - In SQL you can comment on your code like any other language. Comments can appear in one line or take up several lines. Let's take a look at how to comment on your SQL...
SQL EXISTS condition is used in combination with a subquery and is considered satisfied if the subquery returns at least one line. It can be used in the SELECT, INSERT, UPDATE or DELETE...