129 lines
6.9 KiB
Markdown
129 lines
6.9 KiB
Markdown
|
---
|
||
|
|
title: SQL Update Query
|
||
|
|
localeTitle: Consulta de actualización de SQL
|
||
|
|
---
|
||
|
|
## Consulta de actualización de SQL
|
||
|
|
|
||
|
|
### Lo que puede hacer una consulta de actualización
|
||
|
|
|
||
|
|
Una consulta de actualización le da al programador que usa DBA o SQL la capacidad de actualizar muchos registros con un solo comando.
|
||
|
|
|
||
|
|
¡Importante consejo de seguridad! ¡Siempre tenga una copia de respaldo de lo que está a punto de cambiar ANTES de cambiarlo!
|
||
|
|
|
||
|
|
Esta guía:
|
||
|
|
|
||
|
|
* agregar un nuevo campo a la mesa de estudiantes
|
||
|
|
* prueba la lógica para actualizar ese campo con una dirección de correo electrónico asignada por la escuela
|
||
|
|
* actualizar el nuevo campo
|
||
|
|
|
||
|
|
Aquí está la tabla de estudiantes al comenzar este proceso.
|
||
|
|
|
||
|
|
```sql
|
||
|
|
SELECT * FROM student;
|
||
|
|
```
|
||
|
|
|
||
|
|
```text
|
||
|
|
+-----------+------------------------+-----------+------------------+---------------------+---------------------+
|
||
|
|
| studentID | FullName | sat_score | programOfStudy | rcd_Created | rcd_Updated |
|
||
|
|
+-----------+------------------------+-----------+------------------+---------------------+---------------------+
|
||
|
|
| 1 | Monique Davis | 400 | Literature | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|
||
|
|
| 2 | Teri Gutierrez | 800 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|
||
|
|
| 3 | Spencer Pautier | 1000 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|
||
|
|
| 4 | Louis Ramsey | 1200 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|
||
|
|
| 5 | Alvin Greene | 1200 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|
||
|
|
| 6 | Sophie Freeman | 1200 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 |
|
||
|
|
| 7 | Edgar Frank "Ted" Codd | 2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 |
|
||
|
|
| 8 | Donald D. Chamberlin | 2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 |
|
||
|
|
| 9 | Raymond F. Boyce | 2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 |
|
||
|
|
+-----------+------------------------+-----------+------------------+---------------------+---------------------+
|
||
|
|
9 rows in set (0.00 sec)
|
||
|
|
```
|
||
|
|
|
||
|
|
### Alterar la tabla y agregar un nuevo campo.
|
||
|
|
|
||
|
|
```sql
|
||
|
|
ALTER TABLE `fcc_sql_guides_database`.`student`
|
||
|
|
ADD COLUMN `schoolEmailAdr` VARCHAR(125) NULL AFTER `programOfStudy`;
|
||
|
|
```
|
||
|
|
|
||
|
|
La tabla de alumnos después de la alteración se ejecuta.
|
||
|
|
|
||
|
|
```text
|
||
|
|
mysql> SELECT FullName, sat_score, programOfStudy, schoolEmailAdr FROM student;
|
||
|
|
+------------------------+-----------+------------------+----------------+
|
||
|
|
| FullName | sat_score | programOfStudy | schoolEmailAdr |
|
||
|
|
+------------------------+-----------+------------------+----------------+
|
||
|
|
| Monique Davis | 400 | Literature | NULL |
|
||
|
|
| Teri Gutierrez | 800 | Programming | NULL |
|
||
|
|
| Spencer Pautier | 1000 | Programming | NULL |
|
||
|
|
| Louis Ramsey | 1200 | Programming | NULL |
|
||
|
|
| Alvin Greene | 1200 | Programming | NULL |
|
||
|
|
| Sophie Freeman | 1200 | Programming | NULL |
|
||
|
|
| Edgar Frank "Ted" Codd | 2400 | Computer Science | NULL |
|
||
|
|
| Donald D. Chamberlin | 2400 | Computer Science | NULL |
|
||
|
|
| Raymond F. Boyce | 2400 | Computer Science | NULL |
|
||
|
|
+------------------------+-----------+------------------+----------------+
|
||
|
|
9 rows in set (0.00 sec)
|
||
|
|
```
|
||
|
|
|
||
|
|
### PRUEBA de la lógica (paso MUY importante!)
|
||
|
|
|
||
|
|
```sql
|
||
|
|
SELECT FullName, instr(FullName," ") AS firstSpacePosition,
|
||
|
|
concat(substring(FullName,1,instr(FullName," ")-1),"@someSchool.edu") AS schoolEmail
|
||
|
|
FROM student;
|
||
|
|
```
|
||
|
|
|
||
|
|
```text
|
||
|
|
+------------------------+--------------------+------------------------+
|
||
|
|
| FullName | firstSpacePosition | schoolEmail |
|
||
|
|
+------------------------+--------------------+------------------------+
|
||
|
|
| Monique Davis | 8 | Monique@someSchool.edu |
|
||
|
|
| Teri Gutierrez | 5 | Teri@someSchool.edu |
|
||
|
|
| Spencer Pautier | 8 | Spencer@someSchool.edu |
|
||
|
|
| Louis Ramsey | 6 | Louis@someSchool.edu |
|
||
|
|
| Alvin Greene | 6 | Alvin@someSchool.edu |
|
||
|
|
| Sophie Freeman | 7 | Sophie@someSchool.edu |
|
||
|
|
| Edgar Frank "Ted" Codd | 6 | Edgar@someSchool.edu |
|
||
|
|
| Donald D. Chamberlin | 7 | Donald@someSchool.edu |
|
||
|
|
| Raymond F. Boyce | 8 | Raymond@someSchool.edu |
|
||
|
|
+------------------------+--------------------+------------------------+
|
||
|
|
9 rows in set (0.00 sec)
|
||
|
|
```
|
||
|
|
|
||
|
|
_Una nota sobre concat (): en MySQL, este comando se usa para combinar cadenas, no así en otras versiones de SQL (consulte su manual). En este uso funciona así: la subcadena del campo FullName hasta el primer espacio, pero sin incluirlo, se combina con "@ someSchool.edu". En el mundo real, esto DEBERÍA ser mucho más complejo y debería asegurarse de que la dirección de correo electrónico sea única._
|
||
|
|
|
||
|
|
### Haciendo la actualizacion
|
||
|
|
|
||
|
|
Pretenderemos que esto es lo que queremos y actualizaremos la tabla con esta información:
|
||
|
|
|
||
|
|
```sql
|
||
|
|
UPDATE student SET schoolEmailAdr = concat(substring(FullName,1,instr(FullName," ")-1),"@someSchool.edu")
|
||
|
|
WHERE schoolEmailAdr is NULL;
|
||
|
|
```
|
||
|
|
|
||
|
|
¡Éxito!
|
||
|
|
|
||
|
|
```text
|
||
|
|
mysql> SELECT FullName, sat_score, programOfStudy, schoolEmailAdr FROM student;
|
||
|
|
+------------------------+-----------+------------------+------------------------+
|
||
|
|
| FullName | sat_score | programOfStudy | schoolEmailAdr |
|
||
|
|
+------------------------+-----------+------------------+------------------------+
|
||
|
|
| Monique Davis | 400 | Literature | Monique@someSchool.edu |
|
||
|
|
| Teri Gutierrez | 800 | Programming | Teri@someSchool.edu |
|
||
|
|
| Spencer Pautier | 1000 | Programming | Spencer@someSchool.edu |
|
||
|
|
| Louis Ramsey | 1200 | Programming | Louis@someSchool.edu |
|
||
|
|
| Alvin Greene | 1200 | Programming | Alvin@someSchool.edu |
|
||
|
|
| Sophie Freeman | 1200 | Programming | Sophie@someSchool.edu |
|
||
|
|
| Edgar Frank "Ted" Codd | 2400 | Computer Science | Edgar@someSchool.edu |
|
||
|
|
| Donald D. Chamberlin | 2400 | Computer Science | Donald@someSchool.edu |
|
||
|
|
| Raymond F. Boyce | 2400 | Computer Science | Raymond@someSchool.edu |
|
||
|
|
+------------------------+-----------+------------------+------------------------+
|
||
|
|
9 rows in set (0.00 sec)
|
||
|
|
```
|
||
|
|
|
||
|
|
Al igual que con todas estas cosas de SQL, hay MUCHO MÁS que lo que está en esta guía introductoria.
|
||
|
|
|
||
|
|
Espero que al menos esto te dé suficiente para empezar.
|
||
|
|
|
||
|
|
Consulte el manual de su administrador de base de datos y diviértase probando diferentes opciones usted mismo.
|