SQL：仅基于主键列将缺失的行从一个表复制到另一个表

Question

I am trying to copy missing rows from one table to another but only if the primary key field does not exist. Both tables have identical column names but I don't have the number of columns and their names and don't have the primary key column name so it could be "ID" or anything else. Let me explain with an example:

Table 1:

   column 1 (primary key) , Column 2 , Column 3 , ...
   1 , England , London , ...
   2 , France , Paris , ...
   3, Italy , Rome , ...
   4 , Germany , Berlin , ...

Table 2:

    column 1 (primary key) , Column 2 , Column 3 , ...
    1 , Whatever , Whatever , ...
    2 , Whatever , Whatever , ...

I want to copy row 3 and 4 into table 2 so the outcome will be:

Table 2:

    column 1 (primary key) , Column 2 , Column 3 , ...
    1 , Whatever , Whatever , ...
    2 , Whatever , Whatever , ...
    3 , Italy , Rome , ...
    4 , Germany , Berlin , ...

I have tried

   REPLACE INTO table1 SELECT * FROM table2; 

but this will replace the entire table ie Table 2 become exactly like Table 1

Answer 1

You can use insert . . . select insert . . . select insert . . . select :

insert into table2 ( col1, col2 . . . )
    select t1.col1, t1.col2, t1.col3, . . .
    from table1 t1
    where not exists (select 1 from table2 t2 where t2.id = t1.id)

Answer 2

If you just want to ignore rows from table1 with existing primary key in table2 then simplest way is to use INSERT IGNORE syntax:

INSERT IGNORE INTO table2 SELECT * FROM table1;

Note that a row is ignored and not inserted, if there is a duplicate in any UNIQUE KEY (not only PRIMARY).

Documentation: INSERT Syntax

If you use the IGNORE modifier, errors that occur while executing the INSERT statement are ignored. For example, without IGNORE , a row that duplicates an existing UNIQUE index or PRIMARY KEY value in the table causes a duplicate-key error and the statement is aborted. With IGNORE , the row is discarded and no error occurs. Ignored errors generate warnings instead.

Also note that the columns in both tables should be defined in the same order. Actually the tables should have the exactly same schema (same columns with the same data types, length, character sets and collations).