JSON is a free form data exchange format which can cause problems when combined with a strictly typed relational database. Thanks to the folks at https://json-schema.org and the MySQL engineers at Oracle we can no specify required fields, type checks, and range checks.

1. JSON
Validation
Dave Stokes
MySQL Community Manager
MySQL Community Team

2. Dave Stokes
MySQL Community Team
Oracle Corporation
@Stoker
https://elephantdolphin.blogspot.com/
David.Stokes@Oracle.com
Slides are available at Slideshare.net/davestokes
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3. 3
JSON
JSON (JavaScript Object Notation is an open standard file format,
and data interchange format, that uses human-readable text to store
and transmit data objects consisting of attribute–value pairs and array
data types (or any other serializable value). It is a very common data
format, with a diverse range of applications, such as serving as a
replacement for XML in AJAX systems.
JSON is a language-independent data format. It was derived from
JavaScript, but many modern programming languages include code
to generate and parse JSON-format data
-- https://en.wikipedia.org/wiki/JSON

4. { "GNP": 8510700,
"_id": "USA",
"Name": "United States",
"IndepYear": 1776,
"geography": {
"Region": "North America",
"Continent": "North America",
"SurfaceArea": 9363520
},
"government": {
"HeadOfState": "George W. Bush",
"GovernmentForm": "Federal Republic"
},
"demographics": {
"Population": 278357000,
"LifeExpectancy": 77.0999984741211
}
}
4
What does JSON look like?

5. { "GNP": 8510700,
"_id": "USA",
"Name": "United States",
"IndepYear": 1776,
"geography": {
"Region": "North America",
"Continent": "North America",
"SurfaceArea": 9363520
},
"government": {
"HeadOfState": "George W. Bush",
"GovernmentForm": "Federal Republic"
},
"demographics": {
"Population": 278357000,
"LifeExpectancy": 77.0999984741211
}
}
5
What does JSON look like?
KEY : VALUE

6. { "GNP": 8510700,
"_id": "USA",
"Name": "United States",
"IndepYear": 1776,
"geography": {
"Region": "North America",
"Continent": "North America",
"SurfaceArea": 9363520
},
"government": {
"HeadOfState": "George W. Bush",
"GovernmentForm": "Federal Republic"
},
"demographics": {
"Population": 278357000,
"LifeExpectancy": 77.0999984741211
}
}
6
What does JSON look like?
Document enclosed in brackets {}

7. OBJECTS are enclosed in {}
JSON: OBJECTS versus ARRAYS
7
Arrays are enclosed in []

8. 8
Pretty
much
Free Form

9. Strict data types
INT, CHAR, DECIMAL, etc.
Optional
Required columns
Default Values
Constraint Checks, including range
Relational Databases
9
All these features can enforce rigor on you data to
ensure that it is properly formatted BEFORE it
gets saved in the database.
BTW - Much less expensive to keep bad data out
than having to correct it later!

10. 10
Strict
versus
Free Form

11. JSON’s Freeform Can hurt
How would you save email address?
email: user@foo.com
eMail: user@foo.com
e-mail: user@foo.com
electronicMail: user@foo.com
EMail: user@foo.com
eMaIl: user@foo.com
Each of the keys here are unique and valid
Searching for email addresses would require being able to look for all the forms!
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12. 12
Some Examples of keeping data clean
create table percona (id int, name char(25));
insert into percona values ('test');
ERROR: 1136: Column count doesn't match value count at row 1
CREATE table pz (id int, name char(25) not null);
insert into pz (id) values (1);
ERROR: 1364: Field 'name' doesn't have a default value
CREATE TABLE check_plz ( c1 int constraint c1_not_42_error check (c1 <> 42) default 42,
c2 int default 42);
Query OK, 0 rows affected (0.2902 sec)
insert into check_plz (c2) values(NULL);
ERROR: 3819: Check constraint 'c1_not_42_error' is violated.

13. 13
But what if
there was a way
to check JSON data?

14. 14

15. 15

16. 16
The Functions
JSON_SCHEMA_VALID(schema,document)
Validates a JSON document against a JSON schema.
Both schema and document are required.
The schema must be a valid JSON object; the document must be a valid JSON document.
Provided that these conditions are met:
If the document validates against the schema, the function returns true (1);
otherwise, it returns false (0).

17. 17
The Functions
JSON_SCHEMA_VALIDATION_REPORT(schema,document)
Validates a JSON document against a JSON schema.The schema must be a valid JSON object, and the
document must be a valid JSON document. Provided that these conditions are met, the function returns a
report, as a JSON document, on the outcome of the validation. If the JSON document is considered valid
according to the JSON Schema, the function returns a JSON object with one property valid having the
value "true".
If the JSON document fails validation, the function returns a JSON object which includes the properties
listed here:
○ valid: Always "false" for a failed schema validation
○ reason: A human-readable string containing the reason for the failure
○ schema-location: A JSON pointer URI fragment identifier indicating where in the JSON
schema the validation failed (see Note following this list)
○ document-location: A JSON pointer URI fragment identifier indicating where in the JSON
document the validation failed (see Note following this list)
○ schema-failed-keyword: A string containing the name of the keyword or property in the JSON
schema that was violated

18. 18
Simple Example 1 -- the exemplar, the new document, and the test
set @s='{"type": "object",
"properties": {
"myage": {
"type" : "number",
"minimum": 28,
"maximum": 99
}
}
}';
set @d='{ "myage": 33}'
select JSON_SCHEMA_VALID(@s,@d);
+--------------------------+
| JSON_SCHEMA_VALID(@s,@d) |
+--------------------------+
| 1 |
+--------------------------+
1 row in set (0.00 sec)

19. 19
Simple Example 2 -- the exemplar, the new document, and the test
set @s='{"type": "object",
"properties": {
"myage": {
"type" : "number",
"minimum": 28,
"maximum": 99
}
}
}';
set @d='{ "myage": “foo”}'
select JSON_SCHEMA_VALID(@s,@d);
+--------------------------+
| JSON_SCHEMA_VALID(@s,@d) |
+--------------------------+
| 0 |
+--------------------------+
1 row in set (0.00 sec)

20. 20
Simple Example 3 -- the exemplar, the new document, and the test
set @s='{"type": "object",
"properties": {
"myage": {
"type" : "number",
"minimum": 28,
"maximum": 99
}
}
}';
set @d='{ "myage": 16}'
select JSON_SCHEMA_VALID(@s,@d);
+--------------------------+
| JSON_SCHEMA_VALID(@s,@d) |
+--------------------------+
| 0 |
+--------------------------+
1 row in set (0.00 sec)

21. select JSON_PRETTY(JSON_SCHEMA_VALIDATION_REPORT(@s,@d))G
*************************** 1. row ***************************
JSON_PRETTY(JSON_SCHEMA_VALIDATION_REPORT(@s,@d)): {
"valid": false,
"reason": "The JSON document location '#/myage' failed requirement 'minimum'
at JSON Schema location '#/properties/myage'",
"schema-location": "#/properties/myage",
"document-location": "#/myage",
"schema-failed-keyword": "minimum"
}
JSON_SCHEMA_VALIDATION_REPORT()
21

22. CREATE TABLE `testx` (
`col` JSON,
CONSTRAINT `myage_inRange`
CHECK (JSON_SCHEMA_VALID('{"type": "object",
"properties": {
"myage": {
"type" : "number",
"minimum": 28,
"maximum": 99
}
},"required": ["myage"]
}', `col`) = 1)
);
REQUIRE Fields
22

23. CREATE TABLE `testx` (
`col` JSON,
CONSTRAINT `myage_inRange`
CHECK (JSON_SCHEMA_VALID('{"type": "object",
"properties": {
"myage": {
"type" : "number",
"minimum": 28,
"maximum": 99
}
},"required": ["myage"]
}', `col`) = 1)
);
REQUIRE Fields
23
insert into testx values('{"myage":27}');
ERROR 3819 (HY000):
Check constraint 'myage_inRange' is
violated.
insert into testx values('{"myage":97}');
Query OK, 1 row affected (0.02 sec)

24. 24

25. ❏ MySQL Manual -- https://dev.mysql.com/doc/refman/8.0/en/json-validation-functions.html
❏ Understanding JSON Schema -- http://json-schema.org/understanding-json-schema/
❏ Blog post -- https://elephantdolphin.blogspot.com/2019/07/json-schema-validation-with-mysql-
8017.html
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Where to learn more

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29. Then please consider
buying my book on the
JSON data type, how to
use the supporting
functions, and it is filled
with example code to get
you up to speed!
Interested in using JSON with MySQL?
29

30. Thank You!
David.Stokes@oracle.com
@Stoker
slideshare.net/davestokes
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Q&A