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Transact-SQL
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4.6.1 IF…ELSE
ÆäÓï·¨ÈçÏ£º
IF <Ìõ¼þ±í´ïʽ>
<ÃüÁîÐлò³ÌÐò¿é>
[ELSE [Ìõ¼þ±í´ïʽ]
<ÃüÁîÐлò³ÌÐò¿é>]
ÆäÖÐ<Ìõ¼þ±í´ïʽ>¿ÉÒÔÊǸ÷ÖÖ±í´ïʽµÄ×éºÏ£¬µ«±í´ïʽµÄÖµ±ØÐëÊÇÂß¼Öµ“Õæ”»ò“¼Ù”¡£ELSE×Ó¾äÊÇ¿ÉÑ¡µÄ£¬×î¼òµ¥µÄIFÓï¾äûÓÐELSE
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IF…ELSE¿ÉÒÔ½øÐÐǶÌס£
Àý4-9
declare@x
int,@y int,@z int
select @x=1,@y=2, @z=3
if@x>@y
print'x>y' --´òÓ¡×Ö·û´®'x>y'
else if@y>@z
print'y>z'
else print'z>y'
ÔËÐнá¹ûÈçÏÂ
z>y
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4.6.2 BEGIN…END
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BEGIN
<ÃüÁîÐлò³ÌÐò¿é>
END
BEGIN…ENDÓÃÀ´É趨һ¸ö³ÌÐò¿é£¬½«ÔÚBEGIN…ENDÄÚµÄËùÓгÌÐòÊÓΪһ¸öµ¥ÔªÖ´ÐÐBEGIN…END¾³£ÔÚÌõ¼þÓï¾ä£¬ÈçIF…ELSEÖÐʹ
Óá£ÔÚBEGIN…ENDÖпÉǶÌ×ÁíÍâµÄBEGIN…ENDÀ´¶¨ÒåÁíÒ»³ÌÐò¿é¡£
4.6.3 CASE
CASE ÃüÁîÓÐÁ½ÖÖÓï¾ä¸ñʽ:
CASE <ÔËËãʽ>
WHEN <ÔËËãʽ>THEN<ÔËËãʽ>
…
WHEN<ÔËËãʽ>THEN<ÔËËãʽ>
[ELSE<ÔËËãʽ>]
END
CASE
WHEN <Ìõ¼þ±í´ïʽ> THEN <ÔËËãʽ>
WHEN <Ìõ¼þ±í´ïʽ> THEN <ÔËËãʽ>
[ELSE <ÔËËãʽ>]
END
CASEÃüÁî¿ÉÒÔǶÌ×µ½SQLÃüÁîÖС£
Àý4-10£ºµ÷ÕûÔ±¹¤¹¤×Ê£¬¹¤×÷¼¶±ðΪ“1”µÄÉϵ÷8%£¬¹¤×÷¼¶±ðΪ“2”µÄÉϵ÷7%£¬¹¤×÷¼¶±ðΪ“3”µÄÉϵ÷6%£¬ÆäËüÉϵ÷5%¡£
use pangu
update employee
set e_wage =
case
when job_level = ’1’ then e_wage*1.08
when job_level = ’2’ then e_wage*1.07
when job_level = ’3’ then e_wage*1.06
else e_wage*1.05
end
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4.6.4 WHILE…CONTINUE…BREAK
ÆäÓï·¨ÈçÏÂ:
WHILE <Ìõ¼þ±í´ïʽ>
BEGIN
<ÃüÁîÐлò³ÌÐò¿é>
[BREAK]
[CONTINUE]
[ÃüÁîÐлò³ÌÐò¿é]
END
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