84 lines
2.0 KiB
Org Mode
84 lines
2.0 KiB
Org Mode
#+title: Resumen parcial 1
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#+author: Federico Polidoro
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* clase1 DBA: ¿Que hacen?
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son personas con instruccion en la forma en la que funcionan las bases de datos y en especifico la base de datos de la empresa donde trabajan.
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Se encargan de:
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- Crear querys para la obtencion de datos.
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- Crean Y Actualizan las tablas en la base de datos.
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- Son los que garantisan que la dase de datos genere los backups.
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* clase2 SubConsultas
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Es cuando hay una consulta dentro de otra, de las cuales hay diferentes tipos
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** Retornan un valor
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Un ejemplo de una que retorne un valor seria:
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#+begin_src sql
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SELECT Nombre
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FROM Empleado
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WHERE Salario = (
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SELECT MAX(Salario)
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FROM Empleado
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);
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#+end_src
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** Las que retornan una lista de valores
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#+begin_src sql
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SELECT Companyname
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FROM Customers
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WHERE CustomerId IN (SELECT customerId
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FROM Orders
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WHERE Orderdate > “1/1/95)
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#+end_src
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** Subconsultas dentro del FROM
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#+begin_src sql
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SELECT d.DepartamentoId, AVG(d.Salario) AS PromedioSalario
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FROM (
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SELECT DepartamentoId, Salario
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FROM Empleado
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WHERE Salario > 50000
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) AS d
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GROUP BY d.DepartamentoId;
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#+end_src
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* clase3 Subconsulta con update, insert, delete
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** insert
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#+begin_src sql
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INSERT INTO Customers
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(CustomerID,
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CompanyName,
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ContactName,
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ContactTitle,
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Address, City, Region, PostalCode, Country, Phone, Fax)
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SELECT
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SUBSTRING(firstname, 1, 3) + SUBSTRING(lastname, 1, 2) AS CustomerID,
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lastname AS CompanyName,
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firstname AS ContactName,
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title AS ContactTitle,
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address, city, region, postalcode, country, homephone AS Phone, NULL AS Fax
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FROM Employees;
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#+end_src
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** update
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#+begin_src sql
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DELETE FROM [Order Details]
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WHERE OrderID IN (
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SELECT OrderID
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FROM Orders
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WHERE OrderDate = '2005-04-14'
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);
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#+end_src
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** delete
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#+begin_src sql
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UPDATE Products
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SET UnitPrice = UnitPrice + 2
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WHERE SupplierID IN (
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SELECT SupplierID
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FROM Suppliers
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WHERE Country = 'USA'
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);
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#+end_src
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