Codigos Sq

condicion LIKE

El uso de la condicion LIKE nos sirve para validar una cadena de caracteres.La condicion puede ser para numeros o caracteres y tienedos comodines:
% denota cero o mas caracteres_denota un caracter

ejemplo:

select first_name from employees where first_name LIKE ´s%´;

select first_name from employees where first_name LIKe ´-a%´;

select first_name, comision_pctfrom employees where comision_pct is null;para vercuales registros tiene un campo NULL

condiciones logicas

AND
OR
NOT
utilizando el operador and

select employee_id, last_name, job_id,salary from employees where salary>=10000 and job_id LIKE '%man%';

select employee_id,

23/03/2011
select last_name, salary from employees order by last_name,salary desc; esta consulta orde deformarma asendente los nombres y de forma desendente los salarios

El uso de la funcion MOD

select last_name,salary,mod(salary,5000)from employees where job_id='sa_rep';
Funcion AVG (averge)promedio promedio
select avg(salary) from employees;

funcion MAX obtiene el valor maximo de una expresion o columna, ignora los NULL
select max(salary) from employees;

Funcion MIN: arroja elvalor minimo de una tabla, ignorando los null
select min(hire_date), max(hire_date) from employees;
Funcion COUNT cuenta los elementos que existe en una condicion o columna.
select count(*) fromemployees where department_id=50;

select count(commission_pct) from employees where department_id=80;

DISTINC
select count(DISTINCT department_id) from employees;

CLAUSULA GROUP BYconsultas por grupos
select avg(salary) from employees group by department_id;
funcion SUM
select sum(salary)from employees;

25/03/2011

Claususla having filtra grupos
selectdepartment_id,avg(salary) from employees group by department_id having avg(salary)>8000;

select department_id,max(salary) from employees group by department_id having max(salary)>10000;

select job_id,...