How to preserve new lines and formatting while substituting text using sed?

Question

I have a template file like this

$ cat template.txt
QWERTY
~SQL~
ASDFG

I need to substitute the "~SQL~" string in the template file with following text. This text is stored in a variable

SELECT COL1,
       COL2,
       COL3
FROM TABLE;

I tried the following code, but got an error: sed: -e expression #1, char 20: unterminated `s' command

$ query='SELECT COL1,
>        COL2,
>        COL3
> FROM TABLE;'
$ 
$ sed "s/~SQL~/$query/" template.txt
sed: -e expression #1, char 20: unterminated `s' command

If I remove the new lines from "query" , the sed command works fine

$ query='SELECT COL1, COL2, COL3 FROM TABLE;'
$ sed "s/~SQL~/$query/" template.txt
QWERTY
SELECT COL1, COL2, COL3 FROM TABLE;
ASDFG

I would like to preserve the new lines and formatting while substituting the text. How do I achieve this?

Answer 1

You can use this awk:

awk -v q="$query" '/~SQL~/{$0 = q} 1' file
QWERTY
SELECT COL1,
       COL2,
       COL3,
FROM TABLE;
ASDFG

Answer 2

You can do this:

query='SELECT COL1,\n       COL2,\n       COL3\nFROM TABLE;'
sed "s/~SQL~/$query/" template.txt