sql <- "The cat with the bat went to town. He ate the fat mat and wouldn't stop til the sun came up. He was a fat cat that lived with a rat who owned many hats.The cat with the bat went to town. He ate the fat mat and wouldn't stop til the sun came up. He was a fat cat that lived with a rat who owned many hats."
new_cols <- "happy"
gsub('^(.{273})(.+)$', new_cols, sql, perl=TRUE)