MySQL Forums - Docs

Employees sample database (1 reply)

Bob Smith — Sat, 01 Nov 2025 18:25:19 +0000

https://dev.mysql.com/doc/employee/en/sakila-structure.html

The primary key of the departments table in the image on this page is written as dept_name, but it should actually be dept_no

MySql Next-Key Lock Behavior (no replies)

Bill Wen — Mon, 23 Dec 2024 14:46:21 +0000

Regarding the official document version 8.4. Why Next-key behaves like this? "a next-key lock is an index-record lock plus a gap lock on the gap preceding the index record. " For example, I have index on id, query select * from table where id > 3 for update. Other sessions can't insert id = 3. I understand that (2, 3] is the gap preceding the index record but I don't understand why this record need to be locked. Please explain this.

Error in MySQL documentation JSON_VALUE (1 reply)

Derek Wolfe — Wed, 27 Nov 2024 20:08:38 +0000

The documentation is incorrect in that is states the following 2 statements are equivalent.

SELECT JSON_VALUE(json_doc, path RETURNING type);
SELECT CAST(JSON_UNQUOTE(JSON_EXTRACT(json_doc, path)) AS type);

This is incorrect due to how JSON_EXTRACT and JSON_VALUE treat null values differently. This can be easily shown:

SET @object = JSON_OBJECT('index', null);

SELECT JSON_VALUE(@object, '$.index' RETURNING char);
SELECT CAST(JSON_UNQUOTE(JSON_EXTRACT(@object, '$.index')) AS char);

GET DIAGNOSTICS CONDITION 1 returns erroneous info - Big Issue (3 replies)

William Donaldson — Sat, 01 Nov 2025 18:24:26 +0000

I've used Oracle databases since 1998 and recently started big project with MySQL database. When I began migrating database schemas and learning MySQL I was used:

DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
GET DIAGNOSTICS CONDITION 1 e1 = MYSQL_ERRNO, e2 = MESSAGE_TEXT, e3 = RETURNED_SQLSTATE, e4 = SCHEMA_NAME, e5 = CATALOG_NAME;
SELECT e1, e2, e3, e4, e5;
END;

To understand issues I was having. Now much more advanced in MySQL knowledge I realize there is a "BIG ISSUE" with data returned. Verbiage is being added to the MESSAGE_TEXT variable when an error is unknown to MySQL.

I have a Stored Function which checks for conditions before running import process. I am pasting a snippet of One of the conditions:

IF importFileName IS NULL THEN
-- This is an error. Import File must be in table when import processing.
SET processFile = 0;
SIGNAL SQLSTATE
'45000'
SET
MESSAGE_TEXT = `Import File is not found in import_file table. An error has happened.`,
MYSQL_ERRNO = ER_SIGNAL_EXCEPTION;
This is simple and raises an error in the store procedure's - DECLARE EXIT HANDLER FOR SQLEXCEPTION

Here is the BIG ISSUE. Below is the error message returned from the code above.

'Unknown column ''Import File is not found in import_file table. An error has happened.'' in ''field list'''

No where in my code to I ever say 'Unknown column' or ' in 'field list''

MySQL inserted that verbiage into my error message. It does not matter what value I place in SQLSTATE or MYSQL_ERRNO before issuing SIGNAL. MySQL is still replacing MYSQL_ERRNO with 1054 and wraps MESSAGE_TEXT with verbiage 'Unknow column' and ' in 'field list'' on each side.

When I was learning MySQL that inserted message and FALSE MYSQL_ERRNO value had me spend HOURS and HOURS looking for a problem that did not exist. It almost had me talk the client out of using MySQL for the project.

I don't know who is responsible for this HUGE ISSUE but they should be FIRED!

sp cache (no replies)

James jia james — Tue, 09 Jul 2024 08:59:25 +0000

I want to know "To avoid problems caused by metadata changes to tables or views referred to by the prepared statement, the server detects these changes and automatically reprepares the statement when it is next executed. That is, the server reparses the statement and rebuilds the internal structure. Reparsing also occurs after referenced tables or views are flushed from the table definition cache, either implicitly to make room for new entries in the cache, or explicitly due to FLUSH TABLES.

Similarly, if changes occur to objects used by a stored program, the server reparses affected statements within the program." how these words work in mysql codes? Actually i do not see the processing logic of the dependency of sp object,could you please explain it to me or point the core codes for me?

[Documentation]Question about Atomic Data Definition Statement Support (1 reply)

akki An — Thu, 16 May 2024 18:47:08 +0000

"RENAME TABLE operations are only atomic if all named tables use an atomic DDL-supported storage engine."
The above statement appears in the " Atomic Data Definition Statement Support" document, and I think there is a problem. It should be that "RENAME TABLE operations are only atomic if all named tables use an atomic DDL-unsupported storage engine"

restore backup troubles mysqlbackup (no replies)

Tong Li — Wed, 21 Feb 2024 10:28:11 +0000

Hello everyone. Need help please. Backup from previous employer was made with mysqbackup 8.0.26 from enterprise supbscription (meb 8.0.26). Now I don't have this version and official site does not provide meb version 8.0.26 binary. Backup made with meb 8.0.26 doesn't work with further versions like mysqlbackup 8.0.36. What should i do? I can't create new backup, because our db was broken and I cant restore it with mysqlbackup 8.0.36 that is provided by official site, because need mysqlbackup 8.0.26

restore backip troupes (no replies)

Tong Li — Wed, 21 Feb 2024 10:24:47 +0000

MySQL5.7、8.0 InnoDB在 REPEATABLE-READ隔离级别下幻读问题 (no replies)

lk lk — Fri, 29 Dec 2023 07:52:42 +0000

前提条件：
mysql5.7 Or 8.0 版本都存在此问题。存储引擎是：InnoDb，事务隔离级别是：REPEATABLE-READ

表结构、数据：
CREATE TABLE `test` (
`a` int(4) NOT NULL,
`b` int(10) DEFAULT NULL,
PRIMARY KEY (`a`),
KEY `test_b_index` (`b`)
);
insert into test values (1, 1), (2, 3), (3, 6), (4, 8);

事务A: start transaction; select * from test order by a; # 先读取整个表的数据（生成MVCC快照），只能读取到 a=1、2、3、4的数据
事务B: start transaction; insert into test values (5, 7); commit;
事务A: select * from test order by a; # 由于快照已生成，所以查询不到新插入的a=5的数据
事务A: update test set b = 6 where b > 6; # 由于快照已生成，所以查询不到新插入的a=5的数据
事务A: select * from test order by a; rollback; # 能够正常读取到数据 a=5

猜测原因：事务A的更新语句，更改了数据 a=5 的隐藏字段 DB_TRX_ID，上一次修改改数据的事务id，改成了事务A自己的事务id，所以事务A能够查询到新增数据了。
如果是以上原因，我存在疑问的是：事务A的事务id应该比事务B的事务id小，所以不应该让事务A更新到事务B新增的数据

Feedback Report on re-prepare statement not work after renaming table (2 replies)

yadong zhang — Wed, 23 Oct 2024 09:06:34 +0000

Dear mysql
After reading "Caching of Prepared Statements and Stored Programs", I understand that renaming a table name will recompile the prepared statement, but I tested in the mysql-8.2.0 environment and found that the prepared statement was not recompiled after renaming. Is the documentation wrong?

How can I download the html version of MySQL reference manual? (3 replies)

Jun Lai — Thu, 22 Feb 2024 05:09:17 +0000

I don't like pdf format.

fix some typo in world.sql (2 replies)

Alex ----- — Sun, 06 Oct 2024 13:16:37 +0000

1.
Please change in world.sql next lines

INSERT INTO `city` VALUES (144,'Baku','AZE','Baki',1787800);
INSERT INTO `city` VALUES (145,'Gäncä','AZE','Gäncä',299300);
INSERT INTO `city` VALUES (146,'Sumqayit','AZE','Sumqayit',283000);
INSERT INTO `city` VALUES (147,'Mingäçevir','AZE','Mingäçevir',93900);

INSERT INTO `country` VALUES ('AZE','Azerbaijan','Asia','Middle East',86600.00,1991,7734000,62.9,4127.00,4100.00,'Azärbaycan','Federal Republic','Heydär Äliyev',144,'AZ');

to

INSERT INTO `city` VALUES (144,'Bakı','AZE','Bakı',1787800);
INSERT INTO `city` VALUES (145,'Gəncə','AZE','Gəncə',299300);
INSERT INTO `city` VALUES (146,'Sumqayıt','AZE','Sumqayıt',283000);
INSERT INTO `city` VALUES (147,'Mingəçevir','AZE','Mingəçevir',93900);

INSERT INTO `country` VALUES ('AZE','Azerbaijan','Asia','Middle East',86600.00,1991,7734000,62.9,4127.00,4100.00,'Azərbaycan','Republic','İlham Əliyev',144,'AZ');

2.
Remove next line
INSERT INTO `countrylanguage` VALUES ('AZE','Armenian','F',2.0);

is this an error about character set in the docs？ (1 reply)

yunfan zheng — Sat, 11 Nov 2023 07:46:25 +0000

In the document, I can only find the default character and collation for MySQL5.7 are latin1 and latin1_swedish_ci. I want to know if I choose utf8mb4 as the character set, what is the default collation for this character set?

Incomplete/Incorrect documentation of --console option (1 reply)

Giorgi Tsiklauri — Tue, 09 May 2023 12:06:26 +0000

https://dev.mysql.com/doc/refman/8.0/en/server-options.html#option_mysqld_console says about --console option the following(citation below):

"(Windows only.) Cause the default error log destination to be the console. This affects log sinks that base their own output destination on the default destination. See Section 5.4.2, “The Error Log”. mysqld does not close the console window if this option is used."

and I think it's misleading, incomplete and incorrect, because --console doesn't only log error, it actually shows Info and Warning messages as well. If I'll start mysqld.exe without --console, it won't show anything at all.

MySQL 8.0 Secure Deployment Guide — fixes (no replies)

Damian Przysiwek — Mon, 06 Feb 2023 01:20:04 +0000

Reference: https://dev.mysql.com/doc/mysql-secure-deployment-guide/8.0/en/secure-deployment-password-validation.html

In the above guide on Part 2, the descriptions of some of the [mysqld] options are the wrong way around.

"validate_password.number_count" should have the description of "The minimum number of numeric (digit) characters that validate_password requires passwords to have if the password policy is MEDIUM or stronger."

"validate_password.mixed_case_count" should have the description of "The minimum number of lowercase and uppercase characters that validate_password requires passwords to have if the password policy is MEDIUM or stronger. "

In the above guide in Part 3, it mentions using the command "bin/mysqladmin -u root -p version" to get to the MySQL console but it should be "bin/mysql -u root -p"

where can I find the.chm file for MySQL 5.8? (1 reply)

Iftikhar Qureshi — Mon, 30 Jan 2023 10:54:17 +0000

Hello there,
MySQL 5.8 and I were looking for a.chm file for my website( https://siddhgiritubes.net ). If anyone is aware of it, kindly provide the URL.
It displays a PDF, a man, and an information page to explain why it has stopped. a chm file

Request Chinese translation of user manual (no replies)

zhang san — Wed, 11 Jan 2023 16:04:50 +0000

大家好!

官网提供了英文和日语版本的用户手册，但没有中文版本。
https://dev.mysql.com/doc/refman/8.0/en/
长久以来，当我有疑问时，我不得不在充斥着过时信息的第三方博客里寻找答案，希望这种情况能得到改变。
下面是一些我找到的中文文档，但没有一个保持活跃更新。
[5.1] https://www.mysqlzh.com/
[5.7]https://github.com/docs4dev#database
[8.0]https://gitcode.net/dev-cloud/mysql
我能在哪里找到用户手册的原始文档吗？比如说Github或者其他？我希望参与翻译MySQL中文用户手册。
我经常看到一些文档可以在github上编辑和更新，MySQL是否也提供了这样的途径？
https://devguide.python.org/documentation/translating/#translating
https://github.com/python/python-docs-zh-cn
https://explore.transifex.com/python-doc/python-newest/

Hello! every one.

I'm sorry that the following content has the help of translation tools.
The official website provides user manuals in English and Japanese, but there is no Chinese version.
https://dev.mysql.com/doc/refman/8.0/en/
For a long time, when I have questions, I have to look for answers in third-party blogs full of outdated information, hoping that this situation can be changed.
The following are some Chinese documents I found, but none of them remain active and updated.
[5.1] https://www.mysqlzh.com/
[5.7] https://github.com/docs4dev#database
[8.0] https://gitcode.net/dev-cloud/mysql
Where can I find the original document of the user manual? Like Github or something? I hope to participate in the translation of MySQL Chinese user manual.
I often see that some documents can be edited and updated on github. Does MySQL also provide such a way?
https://devguide.python.org/documentation/translating/#translating
https://github.com/python/python-docs-zh-cn
https://explore.transifex.com/python-doc/python-newest/

lost a blank space in this statement (1 reply)

Dee Wu — Thu, 12 Jan 2023 14:54:59 +0000

In this section ( https://dev.mysql.com/doc/refman/8.0/en/connection-compression-control.html ),
"This assumes that thereplica_compressed_protocol" lost a blank space between "the" and "replica_compressed_protocol".

《MySQL 8.0 Reference Manual》 Doc Words Error (1 reply)

Dee Wu — Mon, 05 Dec 2022 23:57:12 +0000

There's an error in the thrid last paragraph of this section ["17.4.8 Switching Sources During Failover"](https://dev.mysql.com/doc/refman/8.0/en/replication-solutions-switch.html). The error's original text is "During this procedure, do not forget to run RESET MASTER on Replica 1 before making Replica 1, Replica 2, and Replica 3 replicas of Source.". I think the first "Replica 1" must be replaced by "Source" in the context. So it it a big mistake which could cause readers misunderstand, even totally opposite!

json_set function dont match doc (2 replies)

wb l — Thu, 08 Dec 2022 03:18:11 +0000

In MySQL doc 8.0, json_set will returns NULL if any argument is NULL. But in my mysql (8.0.31), I found:
select json_set('{}', '$.a', null);
'{"a": null}'

Foreign Keys, Referential Actions: Misleading information about `SET DEFAULT`? (Is actually accepted, but just runs default referential action) (no replies)

Jan Piotrowski — Fri, 04 Nov 2022 23:35:01 +0000

Before I open a bug report, I thought to maybe double check with you here to see if you agree with my observations that the MySQL 8 documentation of the "Referential Actions" section on the "Foreign Keys" page (https://dev.mysql.com/doc/refman/8.0/en/create-table-foreign-keys.html) is wrong:

> SET DEFAULT: This action is recognized by the MySQL parser, but both InnoDB and NDB reject table definitions containing ON DELETE SET DEFAULT or ON UPDATE SET DEFAULT clauses.

I don't think this is correct. The table definition is accepted just fine and the table is created as with any other referential action.

But, I get an error when I run a query that would trigger this referential action and the field is definitely not updated to the default. But the error is also not a special error that tells me that SET DEFAULT is not supported, but it looks to me like this is just the same error as when the default referential action, NO ACTION, is executed.

Here is the SQL to reproduce this:

```
CREATE TABLE `User` (
`id` INTEGER NOT NULL AUTO_INCREMENT,

PRIMARY KEY (`id`)
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- CreateTable
CREATE TABLE `Post` (
`id` INTEGER NOT NULL AUTO_INCREMENT,
`userId` INTEGER NULL DEFAULT 3,

PRIMARY KEY (`id`)
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- AddForeignKey
ALTER TABLE `Post` ADD CONSTRAINT `Post_userId_fkey`
FOREIGN KEY (`userId`) REFERENCES `User`(`id`)
ON DELETE SET DEFAULT ON UPDATE SET DEFAULT;

INSERT INTO `User`(`id`) VALUES (1);
INSERT INTO `User`(`id`) VALUES (3);
INSERT INTO `Post`(`id`, `userId`) VALUES (1, 1);
UPDATE `User` SET `id` = 2 WHERE `id` = 1;
SELECT `id`, `userId`* FROM `Post`;
UPDATE `Post` SET `userId` = 70 WHERE `userId` = 1;
```

This was different in MySQL 5.6 and 5.7 where the `ALTER TABLE` indeed already failed.

Do you agree that the documentation of MySQL 8 was not updated to reflect this changing behavior?

J

Possibly flawed example description for LEAD() and LAG() window functions (no replies)

Daniel Farlow — Thu, 03 Nov 2022 09:48:20 +0000

The MySQL docs entry for the [`LEAD` window function](https://dev.mysql.com/doc/refman/8.0/en/window-function-descriptions.html#function_lead) includes the following example description:

> For example, if `N` is `3`, the return value is `default` for the last two rows.

Shouldn't it be the last *three* rows? If the current row is the third to last row in a partition, then it is not possible to look three rows ahead for a leading value, thus resulting in the `default` value being used for this third to last row (as well as the second to last and actual last rows as well ... hence three rows and not two).

The sample [sales](https://dev.mysql.com/doc/refman/8.0/en/window-functions-usage.html) data set provided in the docs can illustrate what I mean.

The query

```sql
SELECT
S.*,
LEAD(S.profit, 3, -1) OVER(PARTITION BY S.country ORDER BY S.profit DESC) AS 'lead'
FROM
sales S;
```

produces the following result set:

```
+------+---------+------------+--------+------+
| year | country | product | profit | lead |
+------+---------+------------+--------+------+
| 2000 | Finland | Computer | 1500 | -1 |
| 2000 | Finland | Phone | 100 | -1 |
| 2001 | Finland | Phone | 10 | -1 |
| 2000 | India | Computer | 1200 | -1 |
| 2000 | India | Calculator | 75 | -1 |
| 2000 | India | Calculator | 75 | -1 |
| 2001 | USA | Computer | 1500 | 150 |
| 2000 | USA | Computer | 1500 | 100 |
| 2001 | USA | Computer | 1200 | 75 |
| 2001 | USA | TV | 150 | 50 |
| 2001 | USA | TV | 100 | -1 |
| 2000 | USA | Calculator | 75 | -1 |
| 2001 | USA | Calculator | 50 | -1 |
+------+---------+------------+--------+------+
```

The `lead` entries for the `Finland` and `India` `country` partitions all have `-1`, the assigned `default` value, when `N` is `3`. *All* partitions have `-1` as the `lead` value for the last `3` rows of each partition.

The same "issue" appears in the documentation of the `LAG()` window function (i.e., if `N` is `3`, then the return value is `default` for the first *three* rows, not two).

where can I get MySQL 5.7 .chm file (1 reply)

Prashant Nirgun — Mon, 17 Oct 2022 15:57:31 +0000

HI

I was searching for .chm file for MySQL 5.7 & 8 if any one knows it please provide the link. Its showing PDF, Man & Info page why its stop .chm file ?

Docuentation on the new libmysqlclient needs improvement (no replies)

Igor Korot — Sun, 24 Jul 2022 02:02:45 +0000

Hi, ALL,

2 things:

1. There is no indication on how to build libmysqlclient (formerly known as mySQL Connector C) on Windows with MSVC as a Debug version.

Building everything is a cmplete waste of time, especially if I don't need a server -- client only. But the docs doesn't explain how!

The documentation for old product did a perfect ob laying everything out. The current one says - build the server and it will build the library.

2. Documentation on how to use the library is even worse especially on Windows.

The very first sentence in the https://dev.mysql.com/doc/c-api/8.0/en/c-api-building-clients.html#c-api-building-clients-compiling-mysql-clients-on-microsoft-windows states:

To specify header and library file locations, use the facilities provided by your development environment.

What is provided by MSVC?

I know I need mysql.h and the dll, but there are multiple copies of the file available and I don't know which one I shuold use.

I sure hope someone from mySQL foundation will look at this post and fix it or at least confirm and explain here in the meantime

Thank you.

Is it a error in doc? (7 replies)

Stephen Zhao — Wed, 07 Dec 2022 12:14:21 +0000

Document Section: 15.8.12 Enabling Automatic Configuration for a Dedicated MySQL Server

Contents from doc:
-------------------------------------------------------------------------------
innodb_log_files_in_group

The number of log files is configured according to the automatically configured buffer pool size (in gigabytes). Automatic configuration of the innodb_log_files_in_group variable was added in MySQL 8.0.14.

Table 15.11 Automatically Configured Number of Log Files

Buffer Pool Size Number of Log Files
Less than 8GB ROUND(buffer pool size)
8GB to 128GB ROUND(buffer pool size * 0.75)
Greater than 128GB 64
-------------------------------------------------------------------------------

When buffer pool size between 8G and 128G,logfiles#=round(buffer pool size * 0.75);Suppose the buffer pool is 100G, then logfile#=round(100*0.75) = 75, the value greater than the next rank buffer pool size(64).

So, is it a wrong formula or something else?

Broken Link in Documentation (6 replies)

Martie Henry — Thu, 16 Jun 2022 23:46:19 +0000

On this page:
https://dev.mysql.com/doc/refman/8.0/en/faqs-views.html

In this content:
A.6.2.

Is there a discussion forum for MySQL Views?

Yes. See https://forums.mysql.com/list.php?100

There is no forum at https://forums.mysql.com/list.php?100

Is there a discussion forum for MySQL Views?

Using index for skip scan (4 replies)

t k — Thu, 03 Nov 2022 04:12:42 +0000

I was confused as to which had better performance, "index skip scan" or "full table scan" when I read the MySQL document to this point(https://dev.mysql.com/doc/refman/8.0/en/range-optimization.html)

Missing a "FROM" (1 reply)

A SS — Mon, 20 Dec 2021 16:57:14 +0000

Missing a "From" in this example :
https://dev.mysql.com/doc/refman/8.0/en/outer-join-simplification.html
Consider a query of this form, where R(T2) greatly narrows the number of matching rows from table T2:

SELECT * T1 LEFT JOIN T2 ON P1(T1,T2)
WHERE P(T1,T2) AND R(T2)

this sql should be : SELECT * FROM T1 LEFT JOIN T2 ON P1(T1,T2) WHERE P1(T1,T2) AND R(T2)

Missing one{ (1 reply)

lin chen — Wed, 15 Dec 2021 09:58:52 +0000

https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_basic_ok_packet.html

Missing "{" after "if capabilities & CLIENT_SESSION_TRACK"

Grammar error on Loadable Function Reference page (1 reply)

Matthew Peveler — Thu, 09 Dec 2021 12:50:13 +0000

The Loadable Function Reference page (https://dev.mysql.com/doc/refman/8.0/en/loadable-function-reference.html) reads:

> The following table lists each function that is loadable and runtime and provides a short description of each one.

I believe it should be read:

> The following table lists each function that is loadable at runtime and provides a short description of each one.

replacing the "and" between "loadable" and "runtime" with "at".