InfluxQL SHOW 语句
使用 InfluxQL SHOW 语句查询数据库的模式信息。
SHOW RETENTION POLICIES
使用 SHOW RETENTION POLICIES 语句列出与数据库关联的保留策略。每个数据库都有一个保留策略–autogen。
InfluxDB 集群中，保留策略不是数据结构的一部分，但由 InfluxQL 预期并用于完全限定的测量中的 FROM 子句。每个保留策略返回的数据不代表数据库的实际保留相关属性。这些值仅为 InfluxQL 功能兼容性而提供的占位符值。
有关数据库数据保留的信息，请参阅 列出数据库。
SHOW RETENTION POLICIES [ON <database-name>]
示例
-- Show retention policies in the database specified in the query request
SHOW RETENTION POLICIES
-- Show retention policies in a specific database
SHOW RETENTION POLICIES ON "example-database"
SHOW MEASUREMENTS
使用 SHOW MEASUREMENTS 语句列出数据库中的测量。
SHOW MEASUREMENTS [with_measurement_clause] [where_clause] [limit_clause] [offset_clause]
示例
-- Show all measurements
SHOW MEASUREMENTS
-- Show measurements where region tag = 'uswest' AND host tag = 'serverA'
SHOW MEASUREMENTS WHERE "region" = 'uswest' AND "host" = 'serverA'
-- Show measurements that start with 'h2o'
SHOW MEASUREMENTS WITH MEASUREMENT =~ /h2o.*/
SHOW FIELD KEYS
使用 SHOW FIELD KEYS 语句列出测量中的所有字段键。
SHOW FIELD KEYS [from_clause]
示例
-- Show field keys and field value data types from all measurements
SHOW FIELD KEYS
-- Show field keys and field value data types from specified measurement
SHOW FIELD KEYS FROM "cpu"
SHOW TAG KEYS
使用 SHOW TAG KEYS 语句列出测量中的标签键。
SHOW TAG KEYS [from_clause] [where_clause] [limit_clause] [offset_clause]
示例
-- Show all tag keys
SHOW TAG KEYS
-- Show all tag keys from the cpu measurement
SHOW TAG KEYS FROM "cpu"
-- Show all tag keys from the cpu measurement where the region key = 'uswest'
SHOW TAG KEYS FROM "cpu" WHERE "region" = 'uswest'
-- Show all tag keys where the host key = 'serverA'
SHOW TAG KEYS WHERE "host" = 'serverA'
SHOW TAG VALUES
使用 SHOW TAG VALUES 语句列出数据库中指定标签的值。
SHOW TAG VALUES [from_clause] WITH KEY = <tag-expression> [where_clause] [limit_clause] [offset_clause]
默认情况下，SHOW TAG VALUES语句仅返回最近一天的唯一标签值。要修改时间范围，请包含一个基于时间的谓词的WHERE子句。
包含一个FROM子句
我们强烈建议在SHOW TAG VALUES语句中包含一个FROM子句，指定1-50个要查询的表。如果没有FROM子句，InfluxDB查询引擎必须从所有表中读取数据，并从每个表中返回唯一的标签值。
根据数据库中表的数量以及每个表中唯一标签值的数量，省略FROM子句可能会导致查询性能下降、查询超时或不必要的资源分配，这可能会影响其他查询。
示例
-- Show tag values from the cpu measurement for the region tag
SHOW TAG VALUES FROM "cpu" WITH KEY = "region"
-- Show tag values from the cpu measurement for the region tag for a custom time range
SHOW TAG VALUES FROM "cpu" WITH KEY = "region" WHERE time > -7d
-- Show tag values from multiple measurements for the region tag
SHOW TAG VALUES FROM "cpu", "memory", "disk" WITH KEY = "region"
-- Show tag values from the cpu measurement for all tag keys that do not include the letter c
SHOW TAG VALUES FROM "cpu" WITH KEY !~ /.*c.*/
-- Show tag values from the cpu measurement for region & host tag keys where service = 'redis'
SHOW TAG VALUES FROM "cpu" WITH KEY IN ("region", "host") WHERE "service" = 'redis'
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