如何比较2个mysql数据库数据

如何比较2个mysql数据库数据

sql语句：因为MySQL 没有full outer join,所以用left join union all right join来实现

select a.table_schema,

a.table_name,

a.column_name,

b.table_schema,

b.table_name,

b.column_name

from information_schema.columns a

left join information_schema.columns b on a.table_name = b.table_name and a.column_name =

b.column_name andb.table_schema = 'DBNAMe1'

where a.table_schema = 'DBNAME2' and

(b.table_name is null or

b.column_name is null)

union all

select a.table_schema,

a.table_name,

a.column_name,

b.table_schema,

b.table_name,

b.column_name

from information_schema.columns a

left join information_schema.columns b on a.table_name = b.table_name and a.column_name =

b.column_name andb.table_schema = 'DBNAME2'

where a.table_schema = 'DBNAME1' and

(b.table_name is null or

b.column_name is NULL)

MySQL可以使用CASE语句来比较行中的两个数据。根据查询相关公开信息显示：从表中选择*，其中当col1>col2然后col1ELSEcol2结束的情况下；这样就可以比较表中每行col1和col2的值，并返回较大的那一个。

不建议图省事，老老实实写三条比较好。

insert into T2 (A,B,C) select T1.A,T1.B,T1.C from T1 left join T2 on T1.A = T2.A and ( T1.B = T2.B or T1.C = T2.C )

insert into T2 (A,B,C) select T1.A,T1.B,T1.C from T1 left join T2 on T1.B = T2.B and ( T1.A = T2.A or T1.C = T2.C )

insert into T2 (A,B,C) select T1.A,T1.B,T1.C from T1 left join T2 on T1.C = T2.C and ( T1.B = T2.B or T1.A = T2.A )

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