在這種情況下，ASCII()函數的輸出取決於我們是否將NULL作為字串提供，還是只提供NULL。以下範例將示範區別−
mysql> SELECT ASCII(null); +-------------+ | ASCII(null) | +-------------+ | NULL | +-------------+ 1 row in set (0.00 sec) mysql> SELECT ASCII('null'); +---------------+ | ASCII('null') | +---------------+ | 110 | +---------------+ 1 row in set (0.00 sec) mysql> Select ASCII(NULL); +-------------+ | ASCII(NULL) | +-------------+ | NULL | +-------------+ 1 row in set (0.00 sec) mysql> Select ASCII('NULL'); +---------------+ | ASCII('NULL') | +---------------+ | 78 | +---------------+ 1 row in set (0.00 sec)
As we can observe from the above result set that when we will provide NULL or null as a string, ASCII() function will return the number code of the first character i.e. number code of the first character i.e. number code of of N in case of 'NULL' and number code of n in case of 'null', otherwise when we provide simply NULL then it returns NULL as output.
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