将一个表中的第一个值插入另一个表Mysql PHP

Question

I have a table with column x and column ID. I am trying to get the first value from column x and insert it into column y from table b.

here is what I have done and it doesn't work:

$val=mysql_query("SELECT x FROM table_a WHERE id=MIN(id)");
$sql=mysql_query("INSERT INTO table_b (y) VALUES('$val')");

Also when I delete a value from table a column x I have to update the value from table b column y with previous value from table a.

Answer 1

Try with SELECT INTO :

INSERT INTO table_b (y)
     SELECT MIN(table_a.id)
       FROM table_a

In PHP:

$sql=mysql_query('INSERT INTO table_b (y) SELECT MIN(table_a.id) FROM table_a');

Answer 2

use ORDER BY id ASC LIMIT 1 instead of instead of MIN :

$val=mysql_query("SELECT x FROM table_a ORDER BY id ASC LIMIT 1");
$sql=mysql_query("INSERT INTO table_b (y) VALUES('$val')");

or with single query:

$sql=mysql_query("INSERT INTO table_b (y) 
                 (SELECT x FROM table_a ORDER BY id ASC LIMIT 1)");

Answer 3

What your a doing is copying data from one table to another. There is no need for fetching the date first and then inserting it.

Use the INSERT .. SELECT syntax.

Answer 4

try it this way

$val=mysql_query("SELECT x FROM table_a WHERE id=MIN(id)");
$val_res = mysql_fetch_assoc($val);
$sql=mysql_query("INSERT INTO table_b (y) VALUES('".$val_res['x']."')");