Common MySQL errors and solutions summarized painstakingly (II)

MySQL Common error summary table of contents

Chapter one [MySQL Error summary （ Recommended collection )
Chapter two MySQL Error summary （ Recommended collection ）

---

Preface

️ When operating the database , There are always some common mistakes , These errors look different , But everything is the same ,
So I have the idea to sum up these common mistakes , I hope it can help readers who read this article , In this way, this article also has meaning .
If you feel helpful, you can ** Like collection ** support , It would be great if you could pay attention ️‍

One 、MySQL Error summary （ Two ）

1007 - Can’t create database ‘myt3’; database exists

Problem analysis and solutions

• 1 . This is because the current table already exists , Re creation will repeat ,
  The following statement is recommended to create

CREATE DATABASE IF NOT EXISTS myt3 CHARACTER SET 'utf-8';

---

1062 - Duplicate entry 'XXX for key ‘XXX’

Problem analysis and solutions

• 1 . Field sets a unique constraint , When inserting data , Data re conflict

---

1091 - Can’t DROP XXX; check that column/key exists

Problem analysis and solutions

• 1 . This is because when you re create a constraint , An index will be generated automatically （ If you do not specify a name when creating a unique constraint , If it's a single column , The default is the same as the column name ; If it's a composite column , Then default and () The first column in the list has the same name . You can also customize the uniqueness constraint name ）, When we delete constraints , Must be the same as the constraint name to delete
• for example First, query the constraints , And the index name
  SELECT * FROM information_schema.table_constraints WHERE table_name = ‘ Table name l’;
  
  Then delete the constraint
  ALTER TABLE test_notnull DROP INDEX test_unique_phone2;
  

---

1115 - Unknown character set: ‘utf-8’

Problem analysis and solutions

• 1 . This is because the character set is set incorrectly , For example, it is written as utf-8, The right one is utf8
  Write it correctly

CREATE DATABASE IF NOT EXISTS myt3 CHARACTER SET 'utf8';

---

1136 - Column count doesn’t match value count at row 1

Problem analysis and solutions

• 1 . In the process of inserting data , Data and fields do not match （ There may be more data and fewer fields , Or less data , Many fields ）

---

1138 - Invalid use of NULL value

Problem analysis and solutions

• 1 . The reason for this problem is , There are... In the field first NULL , The constraint of the field to be modified is NULL, The constraint fails
  

1166 - Incorrect column name 'owner ’

Problem analysis and solutions

• 1 . The reason is that there are spaces in the fields , Check carefully for deleted spaces

---

Wrong number 1251 Client does not support authentication protocol requested by server;consider upgrading MysQL client

Problem analysis and solutions

• 1 . Because mysql8 In previous versions, the encryption rule was mysql_native_password, And in the mysql8 after , The encryption rule is caching_sha2_password,
• We need to change it

---

> ## 1418 - This function has none of DETERMINISTIC, NO SQL, or READS SQL DATA in its declaration and binary logging is enabled (you *might* want to use the less safe log_bin_trust_function_creators variable)

Problem analysis and solutions

• 1 . This is because... Is turned on by default bin-log（ Ensure that the main memory data is consistent ）, You need to select... When creating the function , Indicates that the program uses SQL Sentence restrictions .
• 
  for example
  

1264 - Out of range value for column ‘f1’ at row 1

Problem analysis and solutions

• 1 . When inserting data , The data exceeds the value range of the data type , example 128 More than the TINYINT Of （-127——128） The scope of the , This type of error will be reported .
• The following is a common value range
  

• ---

1406 - Data too long for column ‘c_gender’ at row 1

Problem analysis and solutions

• 1 . When adding data , Out of range of field , Data can be modified , Or change the length of the field .

---

1423 - Field of view ‘XXX’ underlying table doesn’t have a default value

Problem analysis and solutions

• 1 . This happens when you add or modify view data , First, make it clear that modifying the view will also modify the contents of the data table , Then because when you start creating views , Only some data table fields are selected as views , There are constraints in other fields , For example, it can't be NULL, The transaction cannot be committed .
  give an example
  1 Data table salary Set not to NULL
  
  2 Create view CREATE VIEW v_emp AS SELECT emp_id,emp_name,dept_id FROM emp2; There is no choice at this time salary Field
  3 Insert view operation , Cause errors
  

---

1439 - Display width out of range for column ‘XX’ (max = 64)

Problem analysis and solutions

• 1 . This is because when a table is created or modified , The length range of the data type exceeds ,
  - For example BIT The length range of the type is 1 <= M <= 64 If exceeded 64 There's a problem .

• ---

1452 - Cannot add or update a child row: a foreign key constraint fails (test01_office.emp, CONSTRAINT emp_ibfk_1 FOREIGN KEY (deptid) REFERENCES dept1 (did))

Problem analysis and solutions

• 1 as a result of The referenced fields in the main table There is no such data or the value does not match , So when you add data from a table's foreign key , You can't add it in
• （ For example, the Department field in the employee table , If there is no... In the Department list 10 Department No , The employee table cannot be added to 10 Department No ）

---

1822 - Failed to add the foreign key constraint. Missing index for constraint ‘XXX’ in the referenced table ‘XXX’

Problem analysis and solutions

• 1 . Failed to add foreign key , The reason is that the fields in the main table need The primary key of the primary table or Columns with unique constraints , Can be used as the referenced field

---

3780 - Referencing column ‘deptid’ and referenced column ‘did’ in foreign key constraint ‘emp_ibfk_1’ are incompatible.

Problem analysis and solutions

• 1 . The reason is from the... Of the table deptid Field and main table did word The data type of the segment is inconsistent , And they should have the same logical meaning

---

##4028 - A table must have at least one visible column.

Problem analysis and solutions

• 1 . This is because when creating tables , No fields are set , At least one field must be set to create a table
  Wrong cases

CREATE TABLE IF NOT EXISTS myt4;

---

I hope it will be helpful to your study , I also hope you can give me more support , Leave your love and praise ！
Finally, the best listener wishes everyone can get their favorite Offer

---