What is the Teradata Sample Function?
The SAMPLE function returns a number of rows that were randomly selected. These are the features:
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The Syntax of the Sample Function
SAMPLE [WITH REPLACEMENT]
[RANDOMIZED ALLOCATION]
[WHEN <condition> THEN] {<number of row> | <percentage>}
[...,<number-of-rows> | <percentage>]
[ELSE {<number of rows> | <percentage }
END]
Here are some examples of how to use the SAMPLE function:
100 Random Rows
SELECT * FROM Customer
SAMPLE 100;
10% of Table Rows
SELECT * FROM Customer
SAMPLE .10;
2 Samples with 10% of Table Rows (no Duplicates)
SELECT *
FROM Customer
SAMPLE .1,.1
;
2 Samples with 10 Rows and SAMPLEID
SELECT
t01.* ,
SAMPLEID
FROM Customer t01
SAMPLE 10,10
;
2 Samples with 10% of Table Rows (with Duplicates)
SELECT *
FROM Customer
SAMPLE WITH REPLACEMENT .1,.1
;
2 Samples with Conditional Logic Applied
SELECT *
FROM Customer
SAMPLE
WHEN CustomerId > 1000
THEN .1,.1
ELSE .3,.3 END
;