Copy from one MySQL table to another MySQL table of same database
Suppose you have mydb.mytb and you want to create mydb.mytbcopy

I have five(5) approaches to doing this copy

APPROACH #1

In the mysql client, run the following

USE mydb
CREATE TABLE mytbcopy LIKE mytb;
INSERT INTO mytbcopy SELECT * FROM mytb;


APPROACH #2

MYSQL_USER=root
MYSQL_PASS=rootpassword
MYSQL_CONN="-u${MYSQL_USER} -p${MYSQL_PASS}"
mysql ${MYSQL_CONN} -ANe"CREATE DATABASE IF NOT EXISTS test"
mysqldump ${MYSQL_CONN} mydb mytb | mysql ${MYSQL_CONN} -Dtest
mysql ${MYSQL_CONN} -ANe"ALTER TABLE test.mytb RENAME mydb.mytbcopy"


APPROACH #3

DUMPFILE=/some/path/tabledata.sql
MYSQL_USER=root
MYSQL_PASS=rootpassword
MYSQL_CONN="-u${MYSQL_USER} -p${MYSQL_PASS}"
mysql ${MYSQL_CONN} -ANe"CREATE DATABASE IF NOT EXISTS test"
mysqldump ${MYSQL_CONN} mydb mytb &gt; ${DUMPFILE}
mysql ${MYSQL_CONN} -Dtest &lt; ${DUMPFILE}
rm -f ${DUMPFILE}
mysql ${MYSQL_CONN} -ANe"ALTER TABLE test.mytb RENAME mydb.mytbcopy"


APPROACH #4

MYSQL_USER=root
MYSQL_PASS=rootpassword
MYSQL_CONN="-u${MYSQL_USER} -p${MYSQL_PASS}"
mysqldump ${MYSQL_CONN} mydb mytb | sed 's/mytb/mytbcopy' | mysql ${MYSQL_CONN} -Dmydb


APPROACH #5

DUMPFILE=/some/path/tabledata.sql
MYSQL_USER=root
MYSQL_PASS=rootpassword
MYSQL_CONN="-u${MYSQL_USER} -p${MYSQL_PASS}"
mysqldump ${MYSQL_CONN} mydb mytb | sed 's/mytb/mytbcopy' &gt; ${DUMPFILE}
mysql ${MYSQL_CONN} -Dmydb &lt; ${DUMPFILE}
rm -f ${DUMPFILE}


ANALYSIS


APPROACH #1 is the easiest in terms of steps, but requires pushing 40 million rows into one transaction. This will be the most taxing on the InnoDB Storage Engine.
For the other approaches, mysqldump will send 40 million row in chucks of thousands of rows

APPROACH #2 and APPROACH #3 will mysqldump the table into the test database. After creating the table in the test database, it is subsequently renamed and moved into the original database
APPROACH #4 and APPROACH #5 rename the table using sed against the stream coming from the mysqldump as it echoes the INSERT commands
APPROACH #2 and APPROACH #4 use pipes instead of an output file
APPROACH #3 and APPROACH #5 use an outpuit file for subsequent reload



If you want to copy mydb.mytb to an already existing table mydb.mytbcopy, and the two tables have identical structures:

APPROACH #6

INSERT INTO mytbcopy SELECT * FROM mytb;


Like #APPROACH 1, #APPROACH 6 would have a single transaction of 40 million rows

APPROACH #7

MYSQL_USER=root
MYSQL_PASS=rootpassword
MYSQL_CONN="-u${MYSQL_USER} -p${MYSQL_PASS}"
mysqldump ${MYSQL_CONN} -t mydb mytb | sed 's/mytb/mytbcopy' | mysql ${MYSQL_CONN} -Dmydb


This approaches does not drop the table. It simply generates the INSERTs

EPILOGUE

I cannot give you a time estimate since I do not know the make up of the DB Server, table structure, index layout, and things like these.

GIVE IT A TRY !!!