1. ¿Qué es SQL?

• SQL (Structured Query Language): Lenguaje estandarizado para gestionar bases de datos relacionales.
• Tipos de lenguaje en SQL:
  • Lenguaje de Primera Generación: Código máquina/binario.
  • Lenguaje de Segunda Generación: Ensambladores.
  • Lenguaje de Tercera Generación: Procedurales (FORTRAN, C).
  • Lenguaje de Cuarta Generación: No procedurales (SQL), define el "qué" obtener, no "cómo".

2. Consultas de Selección (SELECT)

SELECT {* | fieldList}
FROM TableName
[WHERE condition]
[ORDER BY fieldList [ASC | DESC]]

• Ejemplos:
  • Todos los campos: SELECT * FROM Publishers;
  • Campos específicos: SELECT Name, City FROM Publishers;
  • Condiciones: SELECT Name, City FROM Publishers WHERE City = "New York";
  • Ordenar: SELECT Name, City FROM Publishers WHERE City <> "New York" ORDER BY Zip DESC;

3. Operadores en WHERE

• Igualdad: =

• Desigualdad: <>

• Comparación: <, <=, >, >=

• Entre valores: BETWEEN

  SELECT * FROM Titles WHERE [Year Published] BETWEEN 1991 AND 1994;
  

• Lista de valores: IN

  SELECT Name, City, Zip FROM Publishers WHERE City IN ("New York", "Paris", "Tacoma");
  

• Coincidencia parcial: LIKE

  SELECT Title FROM Titles WHERE Title LIKE "*SQL*";
  

• Negación: NOT

  SELECT Name, City FROM Publishers WHERE City NOT IN ('New York', 'Paris');
  

4. Sentencias Subordinadas

• WHERE con subconsulta:

  SELECT * FROM Titles WHERE [Year Published] =
      (SELECT [Year Published] FROM Titles WHERE Title LIKE "sql*PC");
  

5. Funciones de Agrupación

• SUM, MIN, MAX, COUNT, AVG:

  SELECT MIN([Year Published]) AS Inicio, MAX([Year Published]) AS Fin FROM Titles WHERE Title LIKE "SQL";
  

6. Agrupación con GROUP BY

SELECT fieldList, COUNT(*)
FROM TableName
GROUP BY fieldList
[HAVING condition]
[ORDER BY COUNT(*) DESC];