MySQL 5.7 is two years old and adoption is growing. The new JSON Data Type shines away as the most talked feature in this version. But they are by no means the only awesome things this it has to offer. Learn how to manipulate JSON fields and how Generated Columns can help you index data and much more with real life examples.

1. Gabriela D'Avila Ferrara
@gabidavila
gabriela.io/feedback | https://joind.in/talk/8884c
Making the most out
of MySQL
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2. @gabidavila
•Developer Advocate
•Lego Hoarder
•@gabidavila
•http://gabriela.io
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$ whoami
•Ada's mom: @ada_doglace

3. @gabidavila
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!

4. @gabidavila
What to expect?
•DDL Changes
•SQL Modes
•Generated Columns
•JSON Data Type
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DDL changes on
InnoDB
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Online DDL Changes
•In place (ALGORITHM=INPLACE)
• Rename index
• VARCHAR from 1B to 255B
• Add a Virtual Column
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Online DDL Changes
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ALTER TABLE addresses
CHANGE COLUMN state state VARCHAR(255);
ALTER TABLE addresses
RENAME INDEX `state_index` TO `ix_state`;

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•Table-copy (ALGORITHM=COPY)
• VARCHAR from 256B to 65535B
• Type conversion
• Add a column* (<=5.7)
Normal DDL changes
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ALTER TABLE with COPY
•1st step: create new table structure with newer definition
•2nd step: copy the data from the original table to the new table
•3rd step: drop the old table and rename the new table
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Normal DDL Change
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ALTER TABLE addresses
CHANGE COLUMN user_id user_id BIGINT;
ALTER TABLE users
ADD COLUMN password_digest VARCHAR(255);

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SQL Modes
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SQL Modes (SELECT @@GLOBAL.sql_mode;)
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On MySQL 5.6:
+--------------------------------------------+
| @@GLOBAL.sql_mode |
+--------------------------------------------+
| STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION |
+--------------------------------------------+
1 row in set (0.00 sec)
On MySQL 5.7 and 8.0:
+-----------------------------------------------------------------------+
| @@GLOBAL.sql_mode |
+-----------------------------------------------------------------------+
| ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE, |
| ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-----------------------------------------------------------------------+
1 row in set (0.00 sec)

13. @gabidavila
MySQL 5.6:
•STRICT_TRANS_TABLES
•NO_ENGINE_SUBSTITUTION
MySQL 5.7 & 8.0:
•STRICT_TRANS_TABLES
•NO_ENGINE_SUBSTITUTION
•ONLY_FULL_GROUP_BY
•NO_ZERO_IN_DATE*
•NO_ZERO_DATE*
•ERROR_FOR_DIVISION_BY_ZERO*
SQL Modes comparison
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Full list of sql_mode

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ERROR_FOR_DIVISION_BY_ZERO
•Write Operation: UPDATE
mysql> UPDATE users SET id = id/0 WHERE id = 2;
ERROR 1365 (22012): Division by 0
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•Read Operation: SELECT
mysql> SELECT id, first_name, last_name, id/0 FROM users WHERE id = 2;
+----+------------+-----------+------+
| id | first_name | last_name | id/0 |
+----+------------+-----------+------+
| 2 | Gabriela | Ferrara | NULL |
+----+------------+-----------+------+
1 row in set, 1 warning (0.00 sec)

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ONLY_FULL_GROUP_BY
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Table `users`
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Field Type Null Key Default Extra
id int(10) unsigned NO PRI auto_increment
first_name varchar(255) NO NULL
last_name varchar(255) NO NULL
email varchar(255) NO NULL
twitter_info json YES

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Repeated emails 5.6
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5.6
SELECT * FROM users GROUP BY email HAVING count(*) > 1
+-------+------------+-----------+---------------------+--------------------------------+
| id | first_name | last_name | email | twitter_info |
+-------+------------+-----------+---------------------+--------------------------------+
| 8965 | Conor | Quitzon | yjacobson@yahoo.com | {"id": 100838242, "url": "http |
| 69772 | Junius | Mante | nkuhlman@gmail.com | {"id": 20039476, "url": "https |
| 66525 | Katelynn | Feil | qgottlieb@gmail.com | {"id": 111644778, "url": "http |
| 92577 | Tillman | Nienow | zzieme@yahoo.com | {"id": 1359073920, "url": "htt |
| 18046 | Guillermo | Lebsack | cdoyle@gmail.com | {"id": 120064855, "url": null, |
+-------+------------+-----------+---------------------+--------------------------------+
5 rows in set (0.65 sec)

19. @gabidavila
Repeated emails
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SELECT * FROM users WHERE email = 'cdoyle@gmail.com'
+-------+------------+-----------+------------------+--------------+
| id | first_name | last_name | email | twitter_info |
+-------+------------+-----------+------------------+--------------+
| 18046 | Guillermo | Lebsack | cdoyle@gmail.com | {...} |
| 20559 | Marietta | Quitzon | cdoyle@gmail.com | {...} |
+-------+------------+-----------+------------------+--------------+
2 rows in set (0.04 sec)

20. @gabidavila
Repeated emails 5.6 & 8.0
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5.7 8.0
mysql> SELECT * FROM `users` GROUP BY `email` HAVING count(*) > 1;
ERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY
clause and contains nonaggregated column ‘social.users.id’ which is
not functionally dependent on columns in GROUP BY clause; this is
incompatible with sql_mode=only_full_group_by
SELECT * FROM users GROUP BY email HAVING count(*) > 1

21. @gabidavila
Why?
"Reject queries for which the select list, HAVING condition, or ORDER
BY list refer to nonaggregated columns that are neither named in the
GROUP BY clause nor are functionally dependent on (uniquely
determined by) GROUP BY columns."
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Hm...
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MySQL to human Translation
This happens because the query is grouping by email and MySQL is magically
trying to “guess” which field it should bring as a result to the other columns (id,
first_name, etc.) and it gives an error since there are more than one result per row
and no aggregator was used to specify the correct value.
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More Info

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The Fix 🛠
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25. @gabidavila
Aggregators!!!
•min(column)
•max(column)
•group_concat(column)
•count(column) or count(*)
•sum(column)
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Old way: using the magic 🎩
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SELECT * FROM users GROUP BY email HAVING count(*) > 1
<?php
// Doctrine
$qb = $entityManager->createQueryBuilder();
$repeatedUsers = $qb->select('*')
->from('users', 'u')
->groupBy('u.email')
->having('count(*) > 1');
// Eloquent
$repeatedUsers = Capsule::table('users')
->select('*')
->groupBy('email')
->havingRaw('count(*) > 1');

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What is the "right"
way? 🤔
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1st step: say what you need
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SELECT
id,
first_name,
last_name,
email,
twitter_info
FROM users
GROUP BY email
HAVING COUNT(*) > 1;
5.6 ✅ Works
5.7 ⛔ Doesn’t Work
8.0 ⛔ Doesn’t Work

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2nd step: adding aggregators
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SELECT
group_concat(id) AS all_users_id,
first_name,
last_name,
email,
twitter_info
FROM users
GROUP BY email
HAVING COUNT(*) > 1;
5.6 ✅ Works
5.7 ⛔ Doesn’t Work
8.0 ⛔ Doesn’t Work

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2nd step: some more column aggregators...
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SELECT
group_concat(id) AS all_users_id,
min(first_name) AS first_name,
last_name,
email,
twitter_info
FROM users
GROUP BY email
HAVING COUNT(*) > 1;
5.6 ✅ Works
5.7 ⛔ Doesn’t Work
8.0 ⛔ Doesn’t Work

31. @gabidavila
3rd step: almost everywhere
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SELECT
group_concat(id) AS all_user_ids,
min(first_name) AS first_name,
min(last_name) AS last_name,
email,
any_value(twitter_info) AS twitter_info
FROM users
GROUP BY email
HAVING COUNT(*) > 1;
5.6 ✅ Works
5.7 ✅ Works
8.0 ✅ Works
You can change the min(column) aggregator to any_value(column)
if the row value for that column doesn't matter

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DEMO
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ONLY_FULL_GROUP_BY trends
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How do I disable it?
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You don't.

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Generated Columns
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Virtual
•No disk space
•In-place change operation
•Value generated on demand and on
every BEFORE triggers
•Faster creation/ slower read
Stored
•Uses disk space
•Copy operation
•Updated on every INSERT and
UPDATE
•Slow creation/ faster read
Types of Generated Columns
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•They only know the table domain
•They have a type
•Allows expressions to be used such as:
• Operators (product * quantity)
• Built-in functions (YEAR(dob))
• Literals ("expression", 1)
•Can be indexed
•Subqueries ARE NOT allowed
•Custom functions ARE NOT supported
•Non-deterministic expressions ARE NOT
supported
Virtual & Stored: common features
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DEMO
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Division by Zero
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Virtual
• Legal
• Returns NULL
Stored
• Illegal
• Returns a "Division by 0" error with these
side effects:
• Not inserting/updating the row
• Not creating the column at all if made
through an ALTER TABLE
Bug #88901

41. @gabidavila
Dependency
•Generated Columns can depend on other generated columns
•Ordering of Generated Columns matter when using another generated column
•It can reference a non-generated column no matter the definition order
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DEMO
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JSON
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JSON
•Stored as Binary, not TEXT
•TEXT fields can be converted
•Accessible by column->"$.value" (JSON_EXTRACT alias)
•Indexing is possible only through Generated Columns (Virtual or Stored)
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Converting TEXT to JSON
•It is costly, uses table COPY operation
•All rows must be valid, else an error occurs
• Use JSON_VALID() before
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DEMO
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Other features
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Features & deprecations
•Passwords can now have an expiration date
•NO_ZERO_DATE, NO_ZERO_IN_DATE, ERROR_FOR_DIVISION_BY_ZERO are deprecated and
being default in STRICT mode in future versions
•Tables now supports more than one trigger per event
•YEAR(2) was deprecated on 5.6 and completely removed on 5.7
•GRANT statement for user creation is deprecated on 5.7 and removed on 8.0
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MySQL 8.0 bits
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MySQL 8.0 bits
•New default encoding
•Data Dictionary
•Users now can have ROLES
•Instantaneously add columns (ALGORITHM=INSTANT)
•CATS instead of FIFO for high concurrency
•JSON partial update
•Window Functions
•Common Table Expressions
•Better Geospatial support
•Use MySQL without SQL (through MySQL Shell)
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51. @gabidavila
Thank you! '.
•Feedback & Slides: gabriela.io/feedback
•Twitter: @gabidavila
•Don't be shy! Come on and talk to me!
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QUESTIONS