For practical matters there is no limit. However some DBMS, e.g. Sybase, have a limit of maximum 50 nesting levels and a maximum of 50 subqueries in each side of a union. However, for practical purposes is difficult to believe that there is a use for a query that involves 5o subqueries.
Jose D. Montero
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T-SQL is Microsoft's version of the generic SQL langauge to be used with, for example, Microsoft SQL Server.
In SQL, the function of the union operator is to combine the result of two or more select-statements. The union operator is a very useful tool when coding SQL.
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There are three types of SQL: 1. Cognos SQL 2. Native SQL 3. Pass-through SQL Cognos SQL Framework Manager generates Cognos SQL in a more efficient manner in order to keep its functionality. It is common for Cognos SQL to be translated into Native SQL before being transmitted to the database for processing. Some actions or functions may not be supported by the database in some instances. Only a portion of the Cognos SQL is transmitted to the database in these situations. As a result, the database handles part of the query and the Cognos server handles the rest. Advantages: Has the ability to include metadata from many sources. Reduce the number of database constraints Interact more effectively with Cognos applications. Disadvantages: You cannot use non standard SQL. Native SQL Databases such as Oracle, SQL Server, and DB2 all support SQL. Using Native SQL in a model query subject with many data sources is not possible. Advantages: All relevant query subjects are optimized for performance. You can utilize SQL that is specific to the database you are using. Disadvantages: You cannot use SQL that the data source does not support for sub queries. The query subject may not be compatible with different database types. Pass-through SQL Allows the usage of Native SQL without regard to the limitations imposed on subqueries by the data source. Subqueries are not processed in Pass-Through SQL query subjects. It is instead supplied directly to the data source that generates query results for each subject. It is important to keep in mind that pass-through SQL is delivered straight to the data source rather than being optimized by the Framework Manager, therefore performance will be lower than with the other query options. Using curly brackets around your SQL statement in a Tabular SQL object causes that SQL statement to be passed through to the database. Cognos has not validated this SQL, so take that into consideration. Step1: Create a Tabular SQL object. Write a statement surrounded with { }. Actual: SELECT * FROM ORDER HEADER Pass-Through: {SELECT * FROM ORDER HEADER} Advantages: You can use any SQL supported by the database. Disadvantages: Framework manager does not have the ability to automatically optimize performance. In some cases, the SQL won't function with another data source.
MOST
Some sample SQL interview questions could be the following 1. Write an SQL query to display the current date. 2. Write a SQL query to name the employees who have worked here for 5 years.
SQL
SQL is a database programming language.By this language we can create ,modify and other updating of our database record.
That's something like: SELECT AVG(column) AS average_value_of_column FROM table;
I would guess the SQL language was considered to be simpler for the programmer.
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Control our any data base with the help of SQL, the professional name of SQL is SEQUEL ( Structure Query English Language)
Transact-SQL is the brand of SQL used by Microsoft SQL Server, Microsoft's most advanced database software.SQL is a language used to operate databases. For example, you could write a SQL query to find the phone numbers for people named "Smith" in a phone database.A database just stores related information in tables organized into rows. For example, a phone book database would have a table of rows where each row contains name, phone number, and address. A database can have multiple tables; so a phone book database would have separate tables for people and businesses.
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