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about "Oracle recommends that unique indexes be created explicitly "

about "Oracle recommends that unique indexes be created explicitly "

2006-06-30       - By qihua wu
Reply:     1     2  

The book of "oracle concept" says
 
 Oracle recommends that unique indexes be created explicitly, using CREATE
UNIQUE INDEX. Creating unique indexes through a primary key or unique
constraint is not guaranteed to create a new index, and the index they create
is not guaranteed to be a unique index.
 
 So under what condition will the created index through primary key or unique
constraint not be a unique index?
 

   
-- ---- ---- ---- ---- ---- -----
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<div>The book of "oracle concept" says</div>  <div>&nbsp;</div>  <div><FONT
size=3><SPAN lang=EN style="mso-ansi-language: EN">Oracle recommends that
unique indexes be created explicitly, using </SPAN><CODE><SPAN lang=EN style=
"mso-ansi-language: EN"><FONT color=#336699>CREATE</FONT></SPAN></CODE><SPAN
lang=EN style="mso-ansi-language: EN"> </SPAN><CODE><SPAN lang=EN style="mso
-ansi-language: EN"><FONT color=#336699>UNIQUE</FONT></SPAN></CODE><SPAN lang=EN
style="mso-ansi-language: EN"> </SPAN><CODE><SPAN lang=EN style="mso-ansi
-language: EN"><FONT color=#336699>INDEX</FONT></SPAN></CODE><SPAN lang=EN style
="mso-ansi-language: EN">. <A style="mso-comment-reference: w_1; mso-comment
-date: 20060630T1638">Creating unique indexes through a primary key or unique
constraint is not guaranteed to create a new index,<STRONG> and the index they
create is not guaranteed to be a unique index</STRONG></A><STRONG>.</STRONG><
/SPAN></FONT></div>  <div><FONT size=3><SPAN lang=EN
style="mso-ansi-language: EN"></SPAN></FONT>&nbsp;</div>  <div><FONT size=3>
<SPAN lang=EN style="mso-ansi-language: EN">So under what condition will the
created index through primary key or unique constraint not be a unique index?<
/SPAN></FONT></div>  <div>&nbsp;</div><p>&#32;
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