database - 什么是表格表达式语句？

Question

当我尝试使用 Azure Data explorer 时，经常使用单词:表格表达式语句。什么是表格表达式语句？它与sql查询语言有什么不同？

Answer 1

首先，表格表达式语句是用kusto查询语言定义的。 Kusto query language与sql查询完全不同。可以引用这个doc差异。

对于表格表达式语句，定义为 here 。以下是其中的一些要点:

The tabular expression statement is what people usually have in mindwhen they talk about queries. This statement usually appears last inthe statement list, and both its input and its output consists oftables or tabular data sets.

Kusto uses a data flow model for the tabular expression statement. Thetypical structure of a tabular expression statement is a compositionof tabular data sources (such as Kusto tables), tabular data operators(such as filters and projections), and potentially renderingoperators.

看起来像这样:

source1 | operator1 | operator2 | renderInstruction

详细示例如下所示:

Logs | where Timestamp > ago(1d) | count