You can either use:
"texta'textb" (APOSTROPHE inside QUOTATION MARKs)
or
'texta'\''textb' (APOSTROPHE text APOSTROPHE, then REVERSE SOLIDUS, APOSTROPHE, then APOSTROPHE more text APOSTROPHE)
I used unicode character names. REVERSE SOLIDUS is more commonly known as backslash.
In the latter case, you close your apostrophe, then shell-quote your apostrophe with a backslash, then open another apostrophe for the rest of the text.