Question of the Day

Rows estimation with OPENJSON

Consider the following script for a Sql Server database with Compatibility Level at least 130 (Sql Server 2016):

create table tjson (
id int primary key,
j1 varchar(max),
j2 varchar(max),
j3 varchar(max));

insert into tjson (id, j1, j2, j3) 
values 
(1,
'[{"c11":"value11A", "c12":"value12A"},{"c11":"value11B", "c12":"value12B"}]',
'[{"c21":"value21A", "c22":"value22A"},{"c21":"value21B", "c22":"value22B"}]',
'[{"c31":"value31A", "c32":"value32A"},{"c31":"value31B", "c32":"value32B"}]');

How many rows does the Query Optimizer estimate for the following query?

select id, c1.c11, c2.c21, c2.c22, c3.c31, c3.c32
from tjson
cross apply openjson(j1) with(
c11 varchar(50) '$.c11',
c12 varchar(50) '$.c12') c1
cross apply openjson(j2) with(
c21 varchar(50) '$.c21',
c22 varchar(50) '$.c22') c2
cross apply openjson(j3) with(
c31 varchar(50) '$.c31',
c32 varchar(50) '$.c32') c3;

 

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