Using placeholders/variables in a sed command

 sed -r "s/CREATE TABLE (\`.*\`)/DROP TABLE IF EXISTS \1\n &/g" dump.sql

test:

kent$  cat t.txt

CREATE TABLE `orders`
...

CREATE TABLE `foo`
...
...

CREATE TABLE `bar`
...


kent$  sed -r "s/CREATE TABLE (\`.*\`)/DROP TABLE IF EXISTS \1\n &/g" t.txt

DROP TABLE IF EXISTS `orders`
 CREATE TABLE `orders`
...

DROP TABLE IF EXISTS `foo`
 CREATE TABLE `foo`
...
...

DROP TABLE IF EXISTS `bar`
 CREATE TABLE `bar`
...

sed '/CREATE TABLE \([^ ]*\)/ s//DROP TABLE IF EXISTS \1; &/'

Find a CREATE TABLE statement and capture the table name. Replace it with 'DROP TABLE IF EXISTS' and the table name, plus a semi-colon to terminate the statement, and a copy of what was matched to preserve the CREATE TABLE statement.

This is classic sed notation. Since you're using bash, there's a chance you're using GNU sed and will need to add --posix to use that notation, or you'll need to fettle the script to use GNU's non-standard sed regexes. I've also not attempted to insert a newline into the output. You can do that with GNU sed if it is important enough to you.

The key points are the parentheses (classically needing to be escaped with a backslash) are the capture mechanism, and backslash-number is the replacement mechanism.

This is called a "back reference". And sed will start numbering the things between the parenthesis. \(...\)

Note the use of backslash as an escape character above.

Ref: https://www.gnu.org/software/sed/manual/html_node/Regular-Expressions.html