更新时间:2024-07-19 GMT+08:00
SELECT查询表数据
本章节主要介绍ClickHouse查询表数据的SQL基本语法和使用说明。
基本语法
SELECT [DISTINCT] expr_list
[FROM [database_name.]table | (subquery) | table_function] [FINAL]
[SAMPLE sample_coeff]
[ARRAY JOIN ...]
[GLOBAL] [ANY|ALL|ASOF] [INNER|LEFT|RIGHT|FULL|CROSS] [OUTER|SEMI|ANTI] JOIN (subquery)|table (ON <expr_list>)|(USING <column_list>)
[PREWHERE expr]
[WHERE expr]
[GROUP BY expr_list] [WITH TOTALS]
[HAVING expr]
[ORDER BY expr_list] [WITH FILL] [FROM expr] [TO expr] [STEP expr]
[LIMIT [offset_value, ]n BY columns]
[LIMIT [n, ]m] [WITH TIES]
[UNION ALL ...]
[INTO OUTFILE filename]
[FORMAT format]
使用示例
--查看ClickHouse集群信息 select * from system.clusters; --显示当前节点设置的宏 select * from system.macros; --查看数据库容量 select sum(rows) as "总行数", formatReadableSize(sum(data_uncompressed_bytes)) as "原始大小", formatReadableSize(sum(data_compressed_bytes)) as "压缩大小", round(sum(data_compressed_bytes) / sum(data_uncompressed_bytes) * 100, 0) "压缩率" from system.parts; --查询test表容量。where条件根据实际情况添加修改 select sum(rows) as "总行数", formatReadableSize(sum(data_uncompressed_bytes)) as "原始大小", formatReadableSize(sum(data_compressed_bytes)) as "压缩大小", round(sum(data_compressed_bytes) / sum(data_uncompressed_bytes) * 100, 0) "压缩率" from system.parts where table in ('test') and partition like '2020-11-%' group by table;
父主题: ClickHouse常用SQL语法