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Fix a mathematical environment issue. #282

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Feb 16, 2023
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Fix a mathematical environment issue. #282

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6 changes: 4 additions & 2 deletions ch2.md
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Expand Up @@ -316,10 +316,12 @@ function getSharks() {
```

在关系代数中：

$$
sharks = σ_{family = "sharks"}(animals)
sharks = \sigma_{family = "sharks"}(animals)
$$
σ（希腊字母西格玛）是选择操作符，只返回符合条件的动物，`family="shark"`。

$\sigma$（希腊字母西格玛）是选择操作符，只返回符合条件的动物，`family="shark"`。

定义 SQL 时，它紧密地遵循关系代数的结构：

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