Stairway Query Store

The Basics - Level 1 of the Stairway to Query Store

  • Stairway Step

Introduction Instead of going straight into the topic of the Query Store, I would like to start this Stairway Series by mentioning a few performance tuning scenarios that are very common to production DBAs. I think most of us have been in one of these situations at some time: An application experiencing slowness after a […]

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2020-10-07 (first published: )

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Question of the Day

STRING_AGG's behavior

Executing the following script (Sql Server 2022), you get the table t0 with 10 rows:
CREATE TABLE t0
( id     INT PRIMARY KEY
, field1 VARCHAR(1000)
, field2 VARCHAR(MAX));
INSERT INTO t0
SELECT
  gs.value
, REPLICATE ('X', 1000)
, REPLICATE ('Y', 1000)
FROM generate_series(1, 10, 1) gs;
GO
What happens if you execute the following statements?
  1. select STRING_AGG(field1, ';') within group (order by id)  from t0;
  2. select STRING_AGG(field2, ';') within group (order by id)  from t0;

See possible answers