php - Checking for duplicates before updating a field -
i developing android application sends http requests
server using php , mysql
.
the user has fill in 2 fields. let's , b these added 2 columns of table (col , col b. however, want add contents of b after that. works fine.
i having problem in checking duplicates of in b. result want user enters , b of content of a+b no duplicates.
this using
$a = $_post['a']; $last_inserted_id = mysql_insert_id(); $updatetable = mysql_query("update table set b=ifnull(concat(b, '$a'), '$a')where _id='$last_inserted_id'");
to make clearer, b contains words not sentence, however, sentence.
so stemmed sentence .. example a="i want learn programming" -$a= "learn programming".
so if b programming .. final result must learn , programming . i'm getting learn programming learn.
if record inserted, could've put data in there in first place. if subsequent request, mysql_insert_id()
cannot trusted, other records might've been inserted.
is there precludes putting data in there in first place?
if want method append existing field, simplify defaulting b
empty string, making ifnull
check on concat
call redundant.
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