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Accepted
Neil P
Asked: 2017-07-08 01:15:40 +0800 CST

SQL 数据仓库 - 是否可以将整个表切换到分区？

  • 772

可能是个愚蠢的问题，但我想知道是否可以将整个表切换为更大表的分区？

我猜不会，因为无法使用检查约束来约束分区边界上的表。

azure-sql-data-warehouse

1 个回答

  1. Best Answer

    Azure SQL 数据仓库不支持检查约束，因此分区切换略有不同。表 DDL 中描述的分区方案（而不是分区方案/函数对）必须在两个表中完全匹配。

    从此处复制的代码示例：

    -- Assume we have a file with the values 1 to 100 in it.

-- Create an external table over it; will have all records in
IF NOT EXISTS ( SELECT * FROM sys.schemas WHERE name = 'ext' )
EXEC ( 'CREATE SCHEMA ext' )
GO


-- DROP EXTERNAL TABLE ext.numbers
IF NOT EXISTS ( SELECT * FROM sys.external_tables WHERE object_id = OBJECT_ID('ext.numbers') )
CREATE EXTERNAL TABLE ext.numbers (
    number          INT             NOT NULL
    )
WITH (
    LOCATION = 'numbers.csv',
    DATA_SOURCE = eds_yourDataSource, 
    FILE_FORMAT = ff_csv
);
GO

-- Create a partitioned, internal table with the records 1 to 50
IF OBJECT_ID('dbo.numbers') IS NOT NULL DROP TABLE dbo.numbers

CREATE TABLE dbo.numbers
WITH (
    DISTRIBUTION = ROUND_ROBIN,
    CLUSTERED INDEX ( number ), 
    PARTITION ( number RANGE LEFT FOR VALUES ( 50, 100, 150, 200 ) )
    )
AS 
SELECT * 
FROM ext.numbers
WHERE number Between 1 And 50;
GO

-- DBCC PDW_SHOWPARTITIONSTATS ('dbo.numbers')


-- CTAS the second half of the external table, records 51-100 into an internal one.
-- As check contraints are not available in SQL Data Warehouse, ensure the switch table
-- uses the same scheme as the original table.
IF OBJECT_ID('dbo.numbers_part2') IS NOT NULL DROP TABLE dbo.numbers_part2

CREATE TABLE dbo.numbers_part2
WITH (
    DISTRIBUTION = ROUND_ROBIN,
    CLUSTERED INDEX ( number ),
    PARTITION ( number RANGE LEFT FOR VALUES ( 50, 100, 150, 200 ) )
    )
AS 
SELECT *
FROM ext.numbers
WHERE number > 50
GO


-- Partition switch it into the original table
ALTER TABLE dbo.numbers_part2 SWITCH PARTITION 2 TO dbo.numbers PARTITION 2;


SELECT *
FROM dbo.numbers
ORDER BY 1;

    HTH

    • 2

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