从VARCHAR创建DOUBLE PRECISION列，其数量为99％...（但包含一些字符串）

I use Postgresql. I have a varchar column RAW_RET, mostly of numbers, and I'm trying to make a new column RET which is DOUBLE PRECISION. The problem is that a few rows of RAW_RET contain text, (Eg. character I use Postgresql. I have a varchar column RAW_R