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SQL stands for the Structured Query Language, which is a programming language created for database. As such, it is used in managing and sharing data, especially the one within the relational database management system. The data is organized into multiple files and tables where the data tables could be related to a common field. Thus, SQL helps in querying (requesting information from the database), controlling the accessibility of data, modifying, and creating the schema for the database system. SQL servers use common software that includes Oracle, MySQL, and Microsoft Access.
The relational database system has one or more objects referred to as tables. The database information or data is stored in the tables. These tables have unique names and comprise of rows and columns. The rows comprise of the data or records of columns while the columns consist of the data type, name of column, and other column attributes.
The tables are created by developing the “create table” statement. As such, the ‘create table’ keywords are entered followed by the name of the table, open parenthesis, the name of the first column, type of data for the column, optional constraints, and a closing parenthesis. An open parenthesis has to be sued at the start of the table while the closing parenthesis is used at the end of column definition. All the definitions of column should be separated with a comma. The names of the table and column should begin with a letter and be followed by numbers, letters, or underscores. However, these should not exceed 30 characters in terms of length.
The data row is added to the table through the development of the insert statement. Thus, the keywords “insert into” are entered followed by the name of the table, open parenthesis, list of the names for columns that are separated using commas, closing parenthesis, keyword values, and list of values with a parenthesis that is enclosed. The entered values are held in rows and match up the names of columns that are specified.
The rows are queried by using the select statement, which helps to query the database. As such, the selected data is retrieved and matches the specified criteria. The names of the column that follow the keyword of select helps in determining the columns to be returned from the results. The name of the table, which follows the keyword ‘from’ helps in making a specification of the queried table that helps in retrieving the results that are desired.
To get the only desired results, the WHERE clause, is used. The clause is essential since it ensures that it is only the records, which match the conditions, of the where clause are returned in the query results. The SELECT statement has to be specified such that it points to the database for querying the data that is required only in order to meet the requirements for business. The ORDER BY expression is used to have the SELECT LIMIT statement established such that the results that are ordered are the only ones that are needed from the target records.
Limiting number of rows
To limit the number of rows that are returned, the SELECT LIMIT statement is developed. As such, the statement ensures that only records from one or more tables are retrieved from a database and the returned records are based on a value that is limited. The development of the SELECT LIMIT statement has to focus on the rows, which the user needs to be returned from the database.
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