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Get started with the U-SQL Catalog in Azure Data Lake Analytics

  • Artikkeli

Important

Azure Data Lake Analytics retired on 29 February 2024. Learn more with this announcement.

For data analytics, your organization can use Azure Synapse Analytics or Microsoft Fabric.

Create a TVF

In the previous U-SQL script, you repeated the use of EXTRACT to read from the same source file. With the U-SQL table-valued function (TVF), you can encapsulate the data for future reuse.

The following script creates a TVF called Searchlog() in the default database and schema:

DROP FUNCTION IF EXISTS Searchlog;

CREATE FUNCTION Searchlog()
RETURNS @searchlog TABLE
(
            UserId          int,
            Start           DateTime,
            Region          string,
            Query           string,
            Duration        int?,
            Urls            string,
            ClickedUrls     string
)
AS BEGIN
@searchlog =
    EXTRACT UserId          int,
            Start           DateTime,
            Region          string,
            Query           string,
            Duration        int?,
            Urls            string,
            ClickedUrls     string
    FROM "/Samples/Data/SearchLog.tsv"
USING Extractors.Tsv();
RETURN;
END;

The following script shows you how to use the TVF that was defined in the previous script:

@res =
    SELECT
        Region,
        SUM(Duration) AS TotalDuration
    FROM Searchlog() AS S
GROUP BY Region
HAVING SUM(Duration) > 200;

OUTPUT @res
    TO "/output/SearchLog-use-tvf.csv"
    ORDER BY TotalDuration DESC
    USING Outputters.Csv();

Create views

If you have a single query expression, instead of a TVF you can use a U-SQL VIEW to encapsulate that expression.

The following script creates a view called SearchlogView in the default database and schema:

DROP VIEW IF EXISTS SearchlogView;

CREATE VIEW SearchlogView AS  
    EXTRACT UserId          int,
            Start           DateTime,
            Region          string,
            Query           string,
            Duration        int?,
            Urls            string,
            ClickedUrls     string
    FROM "/Samples/Data/SearchLog.tsv"
USING Extractors.Tsv();

The following script demonstrates the use of the defined view:

@res =
    SELECT
        Region,
        SUM(Duration) AS TotalDuration
    FROM SearchlogView
GROUP BY Region
HAVING SUM(Duration) > 200;

OUTPUT @res
    TO "/output/Searchlog-use-view.csv"
    ORDER BY TotalDuration DESC
    USING Outputters.Csv();

Create tables

As with relational database tables, with U-SQL you can create a table with a predefined schema or create a table that infers the schema from the query that populates the table (also known as CREATE TABLE AS SELECT or CTAS).

Create a database and two tables by using the following script:

DROP DATABASE IF EXISTS SearchLogDb;
CREATE DATABASE SearchLogDb;
USE DATABASE SearchLogDb;

DROP TABLE IF EXISTS SearchLog1;
DROP TABLE IF EXISTS SearchLog2;

CREATE TABLE SearchLog1 (
            UserId          int,
            Start           DateTime,
            Region          string,
            Query           string,
            Duration        int?,
            Urls            string,
            ClickedUrls     string,

            INDEX sl_idx CLUSTERED (UserId ASC)
                DISTRIBUTED BY HASH (UserId)
);

INSERT INTO SearchLog1 SELECT * FROM master.dbo.Searchlog() AS s;

CREATE TABLE SearchLog2(
    INDEX sl_idx CLUSTERED (UserId ASC)
            DISTRIBUTED BY HASH (UserId)
) AS SELECT * FROM master.dbo.Searchlog() AS S; // You can use EXTRACT or SELECT here

Query tables

You can query tables, such as those created in the previous script, in the same way that you query the data files. Instead of creating a rowset by using EXTRACT, you now can refer to the table name.

To read from the tables, modify the transform script that you used previously:

@rs1 =
    SELECT
        Region,
        SUM(Duration) AS TotalDuration
    FROM SearchLogDb.dbo.SearchLog2
GROUP BY Region;

@res =
    SELECT *
    FROM @rs1
    ORDER BY TotalDuration DESC
    FETCH 5 ROWS;

OUTPUT @res
    TO "/output/Searchlog-query-table.csv"
    ORDER BY TotalDuration DESC
    USING Outputters.Csv();

Note

Currently, you cannot run a SELECT on a table in the same script as the one where you created the table.

Next Steps