For the same table, the QUERY SELECT * FROM T WHERE C1 = 1 causes all the elements of all rows in which the value of column C1 is `1` to be displayed – in relational algebra, a selection is made based on the WHERE clause. This is also known as a horizontal partition, where the rows emitted by a query are limited based on the specified conditions. Processing a SELECT statement according to ANSI SQL would be as follows:[10] You can also retrieve data from multiple columns. For example, to select the first and last names of all students. SQL contains operators and functions for calculating the values of stored values. SQL allows you to use expressions from the select list to project data, as in the following example, which returns a list of books costing more than 100.00, with an additional sales_tax column containing a sales tax amount calculated at 6% of the price. Consider the following SQL statement to learn the clause: A SELECT statement retrieves zero or multiple rows from one or more database tables or database views. In most applications, SELECT is the most commonly used Data Manipulation Language (DML) command. Because 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” that can vary between executions, database versions, and database software.

This feature is called a query optimizer because it is responsible for finding the best possible execution plan for the query within the applicable constraints. A derived table is the use of referencing a SQL subquery in a FROM clause. Essentially, the derived table is a subquery that can be selected or linked. The derived table feature allows the user to reference the subquery as a table. The derived table is also called an online view or select list. Although not in the default value, most DBMSs allow the use of a select clause without a table by specifying that an imaginary table with a row is used. This is mainly used to perform calculations that do not require a table. A query contains a list of columns to include in the final result, usually immediately after the SELECT keyword. An asterisk (“*”) can be used to indicate that the query should return all columns in the queried tables. SELECT is the most complex statement in SQL with optional keywords and clauses, including: MySQL queries are SQL functions that help us access a specific set of records from a database table. We can request any information or data from the database with the clauses or, for example, the SQL statements.

For example, SQL Clauses receives a conditional expression, which can be a column name or a valid term with columns, that supports MySQL functions to calculate the result values of a table in the database. Here are several SQL clauses to execute the statement: The TOP clause is used to determine the number of record rows to display in the result. This TOP clause is used with the SELECT statement, which is implemented specifically for large tables with many records. However, the clause is not supported in many database systems because MySQL supports the LIMIT clause to select a non-limited one. of rows and in Oracle ROWNUM. A better understanding of how things work, better results can be achieved. With basic knowledge of how to execute a Select statement, it will be easier to get the expected result set. In the following example, the SQL statement contains a link between the initial Books table and the derived sales table. This derived table collects information about related book sales using the ISBN to link it to the Books table. Therefore, the derived table provides additional columns to the result set (the number of items sold and the company that sold the books): the following example of a SELECT query returns a list of expensive books.

The query retrieves all rows in the Book table where the price column contains a value greater than 100.00. The result is sorted by title in ascending order. The asterisk (*) in the drop-down list indicates that all columns in the Book table must be included in the result set. In MySQL, we use the SQL SELECT statement to select data from a table in the database. Here, the WHERE clause allows you to filter specific records that exactly match a specified condition. Thus, it helps us to retrieve only the necessary data from the database that meets the given expression conditions. The WHERE clause is used with the SELECT statement and the UPDATE, DELETE, and aggregate functions statements to create the No. records to retrieve from the table. We may also use logical or comparison operators such as LIKE, , = etc. with THE clause to meet certain conditions. A special selection list consisting of a single `*` requests all columns from all tables in the FROM clause.

For example, the SQL SELECT statement returns a result set of records from one or more tables. [1] [2] NOTE: In a SQL SELECT statement, only the SELECT and FROM statements are required. Other clauses such as WHERE, ORDER BY, GROUP BY, HAVING are optional. An unqualified * cannot be combined with other items in the drop-down list. he has to fend for himself. However, a * qualified can be combined with other elements. For example, we can explain this clause through these SQL statements, where we can return the rows with the TOP clause with SELECT and WHERE for different database platforms: you can also use clauses such as WHERE, GROUP BY, HAVING, ORDER BY with the SELECT statement. We will discuss these commandments in future chapters. These SQL clauses support access to the MySQL database and data extraction in many ways by applying any filter that describes the conditions, and if the conditions are appropriate for execution, we get the respective result rows. Here, information from a table that does not meet the conditions is not used. We are dealing with many large databases that are used today in many areas such as online shopping, banking, management, education and other digital domains where a large amount of information is stored and needs to be retrieved from time to time. Thus, SQL statements, functions, operators, and keywords in combination with SQL clauses make access to information correct and manageable for processing different tables in a database.

The most commonly used SQL command is the SELECT statement. The SQL SELECT statement is used to query or retrieve data from a table in the database. A query can retrieve information from specified columns or from all columns in the table. To create a simple SQL SELECT statement, you must specify the name of the column(s) and the name of the table. The entire query is called a SQL SELECT statement. During this step, the processor evaluates what is printed as a result of the query and whether certain functions can be executed on data such as Distinct, Max, Sqrt, Date, Lower, etc. In this case, the select clause prints only the names of the cities and aliases the column city_name with the identifier “City”. The first step in the process is to execute the instructions in the From clause, followed by the Join clause. The result of these operations is to obtain a Cartesian product from our two tables. SELECT is the most common operation in SQL called “query”. SELECT retrieves data from one or more tables or expressions.

DEFAULT SELECT statements have no lasting effect on the database. Some non-standard implementations of SELECT may have persistent effects, such as . B the SELECT INTO syntax provided in some databases. [4] Microsoft SQL Server 2008 and later supports FETCH FIRST, but is considered part of the ORDER BY clause. The ORDER BY, OFFSET, and FETCH FIRST clauses are all required for this use. Note: SQL commands are not case sensitive. The above SELECT statement can also be written to use the ORDER BY clause in SQL to sort records. It is used to organize the result set in ascending or descending order. When we query with the SELECT statement, the result is not in an ordered form. Therefore, the result rows can be sorted when we combine the SELECT statement with the ORDER BY clause.

The above code could return more than ten lines, for example .B. if there are two people of the same age, it could return eleven lines. .