通过识别句点，空格，然后是下一句的大写字母来获取 MySQL 字符串中的第一句

Question

String1 = " Widgets Inc. is the largest widgets producer in the world. It's much bigger than McWidgets Inc."

String2 = " Fidgets Inc is the second largest fidgets producer. It's just behind McFidgets Inc. The CEO of this company loves synergy."

String3 = " Glorious Gagets Co. is considered blah blah jdfglmdslgmldfg. "

For all of the above scenarios, I would like to reliably select the first sentence only . I would use:

[EDIT]: note that there are no real patterns in the sentences.

SUBSTRING_INDEX(string, '. ', 1)

However this would cause issues with the first and third string, as they sometimes have a '.' after the name, and sometimes not.

My thought was to use something like SUBSTRING_INDEX(string, '. [AZ]', 1), and essentially tell it to look for the first '.' which is followed by a space and then any capital letter (ie start of the next sentence), but my SQL-fu is not strong enough yet to figure out how to do that.

Any help would be appreciated!

Answer 1

When you have a fixed pattern, you can use LOCATE to find the index and then use SUBSTRING to remove it. For the startung point you need regular explression, if you don't want to use functions or stored procedures, which you also need for more complex patterns

CREATE TABLE table1 (tex varchar(200))

 INSERT INTO table1 VALUES ("Widgets Inc. is the largest widgets producer in the world. It's much bigger than McWidgets Inc.") ,("Fidgets Inc is the largest fidgets producer in the world. It's much bigger than McFidgets Inc.")

 SELECT SUBSTRING(tex,REGEXP_INSTR(tex, '[AZ]'),LOCATE('producer in the world.',tex)+ 21) FROM table1

\n|  SUBSTRING(tex,REGEXP_INSTR(tex, '[AZ]'),LOCATE('producer in the world.',tex)+ 21) | \n|  :--------------------------------------------------------------------------------- | \n|  Widgets Inc. is the largest widgets producer in the world.  | \n|  Fidgets Inc is the largest fidgets producer in the world.  | \n

db<>fiddle here

Answer 2

K looks like I have a work-around in the absence of actually identifying sentences in the requested manner, ie by somehow including a capital letter check in the substring parameter.

Found a list of abbreviations which would contain a period (ie Co., Inc., Ltd., etc...) and hardcoded to replace them without the period - Co, Ltd, Inc etc... then did the substring as normal. Not ideal but it works.