oracle - substr() & instr()

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.

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個人用例:

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

COLUMN_TYPE: AN APPLE
PARAM_VALUE: AN APPLE~FRUIT
SUBSTR(RF1.PARAM_VALUE,1,INSTR(RF1.PARAM_VALUE,'~')-1): AN APPLE
INSTR(RF1.PARAM_VALUE,'~')+1: 10
這裏用於字段參數化，從一個參數表的某個相應字段中對比取值，對比~前的值，若是一致，那麼取~後的值。