mysql Err1055问题

mysql Err1055问题

试验环境

操作系统：CentOS Linux release 7.3.1611 (Core)

数据库系统： MySQL 5.7.22

问题重现

安装好数据库后尝试创建表，报错：

[Err] 1055 - Expression #1 of ORDER BY clause is not in GROUP BY clause and contains nonaggregated column
'information_schema.PROFILING.SEQ' which is not functionally dependent on columns in GROUP BY clause;
this is incompatible with sql_mode=only_full_group_by

检查发现表正常创建了。

问题分析

查mysql文档得知，mysql从5.7.5开始默认开启ONLY_FULL_GROUP_BY：

对于GROUP BY聚合操作，如果在SELECT中的列，没有在GROUP BY中出现，那么这个SQL是不合法的，因为列不在GROUP BY从句中。

解决方法

方案1、关闭ONLY_FULL_GROUP_BY

查看sql_mole配置：

mysql> select @@sql_mode;
+-------------------------------------------------------------------------------------------------------------------------------------------+
| @@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)

可观察到ONLY_FULL_GROUP_BY处于开启状态

临时关闭ONLY_FULL_GROUP_BY：

mysql> SET sql_mode=(SELECT REPLACE(@@sql_mode,'ONLY_FULL_GROUP_BY',''));
Query OK, 0 rows affected (0.00 sec)

mysql> select @@sql_mode;
+------------------------------------------------------------------------------------------------------------------------+
| @@sql_mode                                                                                                             |
+------------------------------------------------------------------------------------------------------------------------+
| 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)

可看到ONLY_FULL_GROUP_BY被关闭了。

再去修改my.cnf文件，加入下句：

sql_mode ='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION '

方案2、添加any_value()函数

在查询语句中加入any_value函数：

如：
如果查询具有聚合函数且没有GROUP BY子句，则在启用的选择列表，HAVING条件或 ORDER BY列表中 不能包含非聚合列ONLY_FULL_GROUP_BY：

mysql> SELECT name, MAX(age) FROM t;
ERROR 1140 (42000): In aggregated query without GROUP BY, expression
#1 of SELECT list contains nonaggregated column 'mydb.t.name'; this
is incompatible with sql_mode=only_full_group_by

没有GROUP BY，只有一个组，它是不确定的，name为组选择值。ANY_VALUE()如果nameMySQL选择的值不重要，也可以使用这里 ：

SELECT ANY_VALUE(name), MAX(age) FROM t;

小记

官网说法：

MySQL 5.7.5 and up implements detection of functional dependence. If the ONLY_FULL_GROUP_BY SQL mode is enabled (which it is by default), MySQL rejects 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 them. (Before 5.7.5, MySQL does not detect functional dependency and ONLY_FULL_GROUP_BY is not enabled by default. For a description of pre-5.7.5 behavior, see the MySQL 5.6 Reference Manual.)

If ONLY_FULL_GROUP_BY is disabled, a MySQL extension to the standard SQL use of GROUP BY permits the select list, HAVING condition, or ORDER BY list to refer to nonaggregated columns even if the columns are not functionally dependent on GROUP BY columns. This causes MySQL to accept the preceding query. In this case, the server is free to choose any value from each group, so unless they are the same, the values chosen are nondeterministic, which is probably not what you want. Furthermore, the selection of values from each group cannot be influenced by adding an ORDER BY clause. Result set sorting occurs after values have been chosen, and ORDER BY does not affect which value within each group the server chooses. Disabling ONLY_FULL_GROUP_BY is useful primarily when you know that, due to some property of the data, all values in each nonaggregated column not named in the GROUP BY are the same for each group.

You can achieve the same effect without disabling ONLY_FULL_GROUP_BY by using ANY_VALUE() to refer to the nonaggregated column.

The following discussion demonstrates functional dependence, the error message MySQL produces when functional dependence is absent, and ways of causing MySQL to accept a query in the absence of functional dependence.

This query might be invalid with ONLY_FULL_GROUP_BY enabled because the nonaggregated address column in the select list is not named in the GROUP BY clause:

SELECT name, address, MAX(age) FROM t GROUP BY name;

The query is valid if name is a primary key of t or is a unique NOT NULL column. In such cases, MySQL recognizes that the selected column is functionally dependent on a grouping column. For example, if name is a primary key, its value determines the value of address because each group has only one value of the primary key and thus only one row. As a result, there is no randomness in the choice of address value in a group and no need to reject the query.

The query is invalid if name is not a primary key of t or a unique NOT NULL column. In this case, no functional dependency can be inferred and an error occurs:

mysql> SELECT name, address, MAX(age) FROM t GROUP BY name;
ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP
BY clause and contains nonaggregated column 'mydb.t.address' which
is not functionally dependent on columns in GROUP BY clause; this
is incompatible with sql_mode=only_full_group_by

If you know that, for a given data set, each name value in fact uniquely determines the address value, address is effectively functionally dependent on name. To tell MySQL to accept the query, you can use the ANY_VALUE() function:

SELECT name, ANY_VALUE(address), MAX(age) FROM t GROUP BY name;
Alternatively, disable ONLY_FULL_GROUP_BY.

The preceding example is quite simple, however. In particular, it is unlikely you would group on a single primary key column because every group would contain only one row. For addtional examples demonstrating functional dependence in more complex queries, see Section 12.20.4, “Detection of Functional Dependence”.

If a query has aggregate functions and no GROUP BY clause, it cannot have nonaggregated columns in the select list, HAVING condition, or ORDER BY list with ONLY_FULL_GROUP_BY enabled:

mysql> SELECT name, MAX(age) FROM t;
ERROR 1140 (42000): In aggregated query without GROUP BY, expression
#1 of SELECT list contains nonaggregated column 'mydb.t.name'; this
is incompatible with sql_mode=only_full_group_by

Without GROUP BY, there is a single group and it is nondeterministic which name value to choose for the group. Here, too, ANY_VALUE() can be used, if it is immaterial which name value MySQL chooses:

SELECT ANY_VALUE(name), MAX(age) FROM t;

In MySQL 5.7.5 and higher, ONLY_FULL_GROUP_BY also affects handling of queries that use DISTINCT and ORDER BY. Consider the case of a table t with three columns c1, c2, and c3 that contains these rows:

c1 c2 c3
1  2  A
3  4  B
1  2  C

Suppose that we execute the following query, expecting the results to be ordered by c3:

SELECT DISTINCT c1, c2 FROM t ORDER BY c3;

To order the result, duplicates must be eliminated first. But to do so, should we keep the first row or the third? This arbitrary choice influences the retained value of c3, which in turn influences ordering and makes it arbitrary as well. To prevent this problem, a query that has DISTINCT and ORDER BY is rejected as invalid if any ORDER BY expression does not satisfy at least one of these conditions:

• The expression is equal to one in the select list

• All columns referenced by the expression and belonging to the query’s selected tables are elements of the select list

Another MySQL extension to standard SQL permits references in the HAVING clause to aliased expressions in the select list. For example, the following query returns name values that occur only once in table orders:

SELECT name, COUNT(name) FROM orders
  GROUP BY name
  HAVING COUNT(name) = 1;

The MySQL extension permits the use of an alias in the HAVING clause for the aggregated column:

SELECT name, COUNT(name) AS c FROM orders
  GROUP BY name
  HAVING c = 1;

Note
Before MySQL 5.7.5, enabling ONLY_FULL_GROUP_BY disables this extension, thus requiring the HAVING clause to be written using unaliased expressions.

Standard SQL permits only column expressions in GROUP BY clauses, so a statement such as this is invalid because FLOOR(value/100) is a noncolumn expression:

SELECT id, FLOOR(value/100)
  FROM tbl_name
  GROUP BY id, FLOOR(value/100);

MySQL extends standard SQL to permit noncolumn expressions in GROUP BY clauses and considers the preceding statement valid.

Standard SQL also does not permit aliases in GROUP BY clauses. MySQL extends standard SQL to permit aliases, so another way to write the query is as follows:

SELECT id, FLOOR(value/100) AS val
  FROM tbl_name
  GROUP BY id, val;

The alias val is considered a column expression in the GROUP BY clause.

In the presence of a noncolumn expression in the GROUP BY clause, MySQL recognizes equality between that expression and expressions in the select list. This means that with ONLY_FULL_GROUP_BY SQL mode enabled, the query containing GROUP BY id, FLOOR(value/100) is valid because that same FLOOR() expression occurs in the select list. However, MySQL does not try to recognize functional dependence on GROUP BY noncolumn expressions, so the following query is invalid with ONLY_FULL_GROUP_BY enabled, even though the third selected expression is a simple formula of the id column and the FLOOR() expression in the GROUP BY clause:

SELECT id, FLOOR(value/100), id+FLOOR(value/100)
  FROM tbl_name
  GROUP BY id, FLOOR(value/100);

A workaround is to use a derived table:

SELECT id, F, id+F
  FROM
    (SELECT id, FLOOR(value/100) AS F
     FROM tbl_name
     GROUP BY id, FLOOR(value/100)) AS dt;