SQL Server 2017

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CREATE TABLE mytable(
   USER_ID INT
);

insert into mytable values (1);
insert into mytable values (2);
insert into mytable values (3);

DECLARE @USER_ID INT = NULL;

SELECT * 
FROM mytable
WHERE (@USER_ID IS NULL) OR USER_ID = @USER_ID;

SET @USER_ID = 1;

SELECT * 
FROM mytable
WHERE (@USER_ID IS NULL) OR USER_ID = @USER_ID;


USER_ID


1

2

3




USER_ID


1


select * from docs;
Msg 208 Level 16 State 1 Line 1
Invalid object name 'docs'.

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-- ① Execution Plans 
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-- result can be pasted into https://explain.depesz.com
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vacuum analyze;
Msg 2812 Level 16 State 62 Line 1
Could not find stored procedure 'vacuum'.

explain (analyze,buffers)
select max('Do this to get execution plans and stats')
from docs d1 cross join docs d2;
Msg 102 Level 15 State 1 Line 1
Incorrect syntax near 'analyze'.

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-- ② Graphs
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-- "§Chart§" is a magic value to recognize the output as graph data
-- this is a live dbfiddle stats graph but any data can be used
-- dbfiddle stats are only accessible inside the Postgres 9.6 backend
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select to_char(date_trunc('day',history_hour_at),'YYYY-MM-DD') "§Chart§"
     , coalesce(sum(distinct_ip) filter (where rdbms_code~'^sqlserver'),0) "SQL Server"
     , coalesce(sum(distinct_ip) filter (where rdbms_code~'^postgres'),0) "Postgres"
     , coalesce(sum(distinct_ip) filter (where rdbms_code~'^oracle'),0) "Oracle"
     , coalesce(sum(distinct_ip) filter (where rdbms_code~'^maria'),0) "MariaDB"
     , coalesce(sum(distinct_ip) filter (where rdbms_code~'^sqlite'),0) "SQLite"
from stats.rdbms
group by date_trunc('day',history_hour_at)
order by 1;
Msg 195 Level 15 State 10 Line 8
'date_trunc' is not a recognized built-in function name.