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Fix a mathematical environment issue.

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Ze Wang 2023-02-16 04:41:37 -05:00 committed by GitHub
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@ -316,10 +316,12 @@ function getSharks() {
``` ```
在关系代数中： 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： 定义 SQL 时，它紧密地遵循关系代数的结构：