58 lines
2.2 KiB
Markdown
58 lines
2.2 KiB
Markdown
---
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title: SQL Aliases
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localeTitle: SQL别名
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---
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## SQL别名
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## 使用AS分配有意义或更简单的名称
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您可以使用AS为您选择的数据列或已计算的数据分配名称。
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```sql
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SELECT user_only_num1 AS AgeOfServer, (user_only_num1 - warranty_period) AS NonWarrantyPeriod FROM server_table
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```
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这导致输出如下。
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```text
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+-------------+------------------------+
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| AgeOfServer | NonWarrantyPeriod |
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+-------------+------------------------+
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| 36 | 24 |
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| 24 | 12 |
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| 61 | 49 |
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| 12 | 0 |
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| 6 | -6 |
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| 0 | -12 |
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| 36 | 24 |
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| 36 | 24 |
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| 24 | 12 |
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+-------------+------------------------+
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```
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您还可以使用AS为表分配名称，以便在连接中更容易引用。
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```sql
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SELECT ord.product, ord.ord_number, ord.price, cust.cust_name, cust.cust_number FROM customer_table AS cust
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JOIN order_table AS ord ON cust.cust_number = ord.cust_number
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```
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这导致输出如下。
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```text
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+-------------+------------+-----------+-----------------+--------------+
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| product | ord_number | price | cust_name | cust_number |
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+-------------+------------+-----------+-----------------+--------------+
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| RAM | 12345 | 124 | John Smith | 20 |
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| CPU | 12346 | 212 | Mia X | 22 |
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| USB | 12347 | 49 | Elise Beth | 21 |
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| Cable | 12348 | 0 | Paul Fort | 19 |
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| Mouse | 12349 | 66 | Nats Back | 15 |
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| Laptop | 12350 | 612 | Mel S | 36 |
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| Keyboard| 12351 | 24 | George Z | 95 |
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| Keyboard| 12352 | 24 | Ally B | 55 |
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| Air | 12353 | 12 | Maria Trust | 11 |
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+-------------+------------+-----------+-----------------+--------------+
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``` |