Oracle 函数_substr

 

    substr('This is a test', 6, 2)        wouldreturn 'is'
    substr('This is a test', 6)            wouldreturn'is a test'
    substr('TechOnTheNet', 1, 4)    wouldreturn'Tech'
    substr('TechOnTheNet',-3, 3)    wouldreturn 'Net'
    substr('TechOnTheNet',-6, 3)    wouldreturn 'The'
    substr('TechOnTheNet',-8, 2)    wouldreturn 'On'