SQL Intercept string

1. Intercept string from left
Left (str, length)
Description: Left (truncated field, intercept length)
Example: Select Left (content,200) as abstract from my_content_t

2, starting from the right to intercept the string
Right (str, length)
Description: Right (truncated field, intercept length)
Example: Select Right (content,200) as abstract from my_content_t

3. Intercepting strings
SUBSTRING (str, POS)
SUBSTRING (str, pos, length)
Description: Substring (intercepted field, starting from the first intercept)
SUBSTRING (intercepted field, starting from the first intercept, intercept length)
Example: Select substring (content,5) as abstract from my_content_t
Select substring (content,5,200) as abstract from my_content_t
(Note: If the number of digits is negative, 5 is the number of digits from the back to the end of the string or the length of the Intercept)

4. Intercept strings by keyword
Substring_index (Str,delim,count)
Description: Substring_index (the number of occurrences of the intercepted field, keywords, keywords)
Example: Select Substring_index ("Blog.jb51.net", ". ", 2) as abstract from my_content_t
Results: blog.jb51
(Note: If the number of occurrences of a keyword is negative, 2 is the inverse from the back to the end of the string)

SQL Intercept string