Common MySQL errors and solutions summarized painstakingly (I)

MySQL Common error summary table of contents

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

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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 （ One ）

1052 - Column ‘XXX’ in field list is ambiguous

Problem analysis and solutions

• 1 . In multi-table queries , Fields that appear in multiple tables , This field does not indicate which table field it belongs to , Lead to SQL I don't know the segment of that table . You need to indicate the table in front of each field

1054 - Unknown column ‘XXX’ in ‘where clause’

Problem analysis and solutions

• 1 . SQL sentence WHERE The column name inside is incorrectly written （ For example, column name addition error ） Change column names .
• 2 . Or the parameters are not written correctly , Not in accordance with specifications

add to （ Inquire about ） When data appears 1054 - Unknown column ‘myt3’ in ‘field list’

Problem analysis and solutions

• 1 . When transmitting data , Wrong data type , For example String and date type variables need to add a pair ‘’ Single quoted data , No addition
• 2 . The column name in the data table is incorrectly written （ For example, column name addition error ） Change column names .

1055 - Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column ‘XXX’ which is not functionally

dependent on columns in GROUP BY clause; this is incompatible with
sql_mode=only_full_group_by

Problem analysis and solutions

• 1 . The online method is to modify the configuration , That will not solve the fundamental problem , I just don't report any mistakes . Careful analysis of the data is due to the existence of duplication , amount to group by It doesn't work, so this problem arises
  for example

By Department id grouping , But there must be all salary, Equivalent to department grouping , But nothing else , Lead to GROUP BY No effect

Write it correctly （ Don't repeat , Give Way GROUP BY invalid ）

• 2 .GROUP BY The following conditions are misspelled , If you want to rely on multiple field grouping, you should use ‘ ,’ Separate , Out of commission AND,OR Predicates for judging between conditions , If you want to filter groups
  Use . HAVING.
• 3 . Be careful SELECT The fields of non group functions appearing in must be declared in GROUP BY in ,GROUP BY Fields declared in can not appear in SELECT in .

1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use

near ‘user test1’ at line 1

Problem analysis and solutions

• 1 .SQL sentence Writing errors , Locate the prompt inside the single quotation mark , To modify SQL sentence （ Check your spelling carefully 、 Punctuation ）
  for example
  
• 2 . It may be that the position of keywords is reversed , For example GROUP BY The statement is not placed in FROM、WHERE Back or LIMIT Front wait

1111 - Invalid use of group function

Problem analysis and solutions

• 1 . Invalid usage of aggregate function , This problem arises because in WHERE The filter conditions contain aggregate functions , and GROUP BY When used with aggregate functions, you need HAVING.
• 2 . The aggregate function is nested , Aggregate functions cannot be nested .
  

## 1146 - Table 'test1.sys_menu' doesn't exist

Problem analysis and solutions

• 1 . The data table is not in the database , Check the data table for write errors ;
• 2 . Check if another database is being used , The location of the database is incorrect , Causes a table in this database to be queried in another database .

1140 - In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column 'XXX; this is incompatible

with sql_mode=only_full_group_by

Problem analysis and solutions

• 1 . stay MySQL5.7.5 after , The default is on ONLY_FULL_GROUP_BY, there SQL Nonstandard causes this error to occur ,
  because group by after , Some of the data returned is indeterminate , That's why this error occurs .
• 2 . Filter conditions are not used , Only the function is used alone , At the same time, there are other fields in the query ,
  example
  SELECT job_id,COUNT()
  -> FROM employees;
  
  count（） Is a many to one function , Return the number of fields in the result , There are no restrictions on filtering , The total number of rows in the database is displayed , It can't be done SELECT Many to one results , So report an error , Need to add filter conditions or SELECT COUNT() FROM employees;.

In short Anything that doesn't appear in group by Attribute in clause , If you want to appear in select In clause , Then the attribute can only appear inside the aggregate function

1241 - Operand should contain 1 column(s)

Problem analysis and solutions

• 1 . our sql Statement has one more column of operands , Or the given parameter format is incorrect , modify SQL sentence

  HAVING AVG(salary)<=ALL(SELECT department_id,AVG(salary) 'avg_salary' FROM employees)

there AVG（salary） Corresponds to two columns of operands , So there is the problem of not knowing who to match .

1242 - Subquery returns more than 1 row

Problem analysis and solutions

• 1 . Subquery result is more than one row , Modify the results of the subquery

1248 - Every derived table must have its own alias

Problem analysis and solutions

• 1 . The derived table you set does not have an alias , Alias the derived table , Note that multiple derived tables are nested , Each derived table needs to be aliased .

1305 - FUNCTION database .XXX does not exist

Problem analysis and solutions

• 1 . Function does not exist , Description in SQL sentence The function is not written correctly , This causes the function to search from the database , Not from the library ,
  Double check the name of the function .

SQL Statement null value participates in operation , The result is wrong

Problem analysis and solutions

• 1 . Because in SQL Inside null It's not equal to 0, Use when NULL When participating in a progressive operation , Will result in less than ideal answers to the data ,
  Need to call IFNULL( contain NULL Field ,0) function , When null Appear with 0 Instead of .

Subquery returns more than 1 row

Problem analysis and solutions

• 1 . This is because the return result of the subquery is multiple rows , Unable to match the problem that occurred , Modify subquery

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