110 lines
3.2 KiB
Markdown
110 lines
3.2 KiB
Markdown
---
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title: SQL Replace VIEW Statement
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localeTitle: SQL替换VIEW语句
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---
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## SQL替换VIEW语句
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## 介绍
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View是一个数据库对象，它在一个或多个表中显示数据。用于创建视图的相同SQL语句也可用于替换现有视图。
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本指南将使用略有不同且名称不同的视图更新（替换）现有视图“programming-students-v”。
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安全提示：在对模式进行更改之前始终备份模式。
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### 一般sytax
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```sql
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CREATE OR REPLACE VIEW view_name AS
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SELECT column1, column2, ...
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FROM table_name
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WHERE condition;
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```
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### SQL用于创建视图和当前数据
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```sql
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create view `programming-students-v` as
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select FullName, programOfStudy
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from student
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where programOfStudy = 'Programming';
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```
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```sql
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select * from `programming-students-v`;
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```
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当前数据：
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```text
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+-----------------+----------------+
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| FullName | programOfStudy |
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+-----------------+----------------+
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| Teri Gutierrez | Programming |
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| Spencer Pautier | Programming |
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| Louis Ramsey | Programming |
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| Alvin Greene | Programming |
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| Sophie Freeman | Programming |
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+-----------------+----------------+
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5 rows in set (0.00 sec)
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```
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现有视图的列表：
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```sql
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SHOW FULL TABLES IN fcc_sql_guides_database WHERE TABLE_TYPE LIKE 'VIEW';
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```
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```text
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+-----------------------------------+------------+
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| Tables_in_fcc_sql_guides_database | Table_type |
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+-----------------------------------+------------+
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| programming-students-v | VIEW |
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| students-contact-info_v | VIEW |
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| students_dropme_v | VIEW |
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+-----------------------------------+------------+
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3 rows in set (0.00 sec)
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```
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### 替换视图
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```sql
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create or replace view `programming-students-v` as
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select FullName, programOfStudy, sat_score
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from student
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where programOfStudy = 'Programming';
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```
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```sql
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select * from `programming-students-v`;
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```
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注意：视图现在显示sat\_score。
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```text
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+-----------------+----------------+-----------+
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| FullName | programOfStudy | sat_score |
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+-----------------+----------------+-----------+
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| Teri Gutierrez | Programming | 800 |
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| Spencer Pautier | Programming | 1000 |
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| Louis Ramsey | Programming | 1200 |
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| Alvin Greene | Programming | 1200 |
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| Sophie Freeman | Programming | 1200 |
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+-----------------+----------------+-----------+
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```
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注意：视图列表没有更改，我们的视图被替换。
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```text
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mysql> SHOW FULL TABLES IN fcc_sql_guides_database WHERE TABLE_TYPE LIKE 'VIEW';
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+-----------------------------------+------------+
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| Tables_in_fcc_sql_guides_database | Table_type |
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+-----------------------------------+------------+
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| programming-students-v | VIEW |
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| students-contact-info_v | VIEW |
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| students_dropme_v | VIEW |
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+-----------------------------------+------------+
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3 rows in set (0.00 sec)
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```
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\*与所有这些SQL事物一样，它们比本入门指南中的内容更多。我希望这至少足以让你开始。请参阅您的数据库管理员手册，并自己尝试不同的选项。 |