Apache Cloudberry 构建于 PostgreSQL 之上，遵循 SQL 标准来进行数据定义、操作和分析。要有效地编写查询语句，需要了解决定 SQL 语法和语义的一些基本规则。
本文档介绍在 Apache Cloudberry 中构建 SQL 查询所需掌握的核心概念，包括 SQL 语言结构、值表达式、聚合函数 和窗口函数、子查询以及表达式的求值规则。这些内容分别对应 SQL 查询的不同组成部分，能够帮助你编写准确、高效且表达能力强的查询语句。
本页链接的子主题提供了更详细的说明和示例，帮助你编写与 Cloudberry 引擎高度兼容的 SQL 查询。
Apache Cloudberry is an effort undergoing incubation at The Apache Software Foundation (ASF), sponsored by the Apache Incubator. Incubation is required of all newly accepted projects until a further review indicates that the infrastructure, communications, and decision making process have stabilized in a manner consistent with other successful ASF projects. While incubation status is not necessarily a reflection of the completeness or stability of the code, it does indicate that the project has yet to be fully endorsed by the ASF.
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