1. substr()

Syntax:

SUBSTR (string,start_position,[length_of_substring])

eg:

substr('This is a test',6,2)     would return 'is'

remarks:

• The original string is assumed to start at position one (1).
• If substring_length is omitted,then Oracle returns all characters to the end of char.
• If substring_length is less than 1,then Oracle returns null.

2. instr()

Syntax:

instr(string,substring,[position],[occurrence])

eg:

select instr('corporate floor','or',3,2) from dual;  would return '14'

remarks:

• The default values of both position and occurrence are 1,meaning Oracle begins searching at the first character of string for the first occurrence of substring.
• The return value is relative to the beginning of string,regardless of the value of position.

我的用例:

CASE UPPER(T1.COLUMN_TYPE)
    WHEN SUBSTR(RF1.PARAM_VALUE,1,INSTR(RF1.PARAM_VALUE,'~')-1) THEN SUBSTR(RF1.PARAM_VALUE,'~')+1)
    ELSE T1.PRODUCT_TYPE_DESC
END AS PRODUCT_TYPE

COLUMN_TYPE: AN APPLE PARAM_VALUE: AN APPLE~FRUITSUBSTR(RF1.PARAM_VALUE,'~')-1): AN APPLE INSTR(RF1.PARAM_VALUE,'~')+1: 10这里用于字段参数化，从一个参数表的某个相应字段中对比取值，对比~前的值，如果一致，那么取~后的值。