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)

List A

List B

for(int i=0i<A.size()i++)

if(!B.contains(A.get(i)))

insert(A.get(i))

在插入数据库之前先做一个判断

boolean ifExists=false

String insertUser,strSql="select user from emp"

stmt.executeUpdate(sql)

while( stmt.next){

if(insertUser.equals(stmt.getString("user"))){

ifExists=true

break

}

}

if( ifExists){

system.out.println("用户已存在")

}else{

String sql = "insert into emp values('"+ num +"' )" stmt.executeUpdate(sql)

System.out.println("恭喜你同志添加成功!")

}

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