mysql存储过程之代码块条件控制迭代.docx
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mysql存储过程之代码块条件控制迭代.docx
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mysql存储过程之代码块条件控制迭代
MySQL存储过程之代码块、条件控制、迭代
1,代码块
代码顺序Java代码
程序代码可以给代码块加lebel,这样END匹配比较直
观,还可以用LEAVE语句来终结代码块:
Java代码
varaiableandconditiondeclarations
cursordeclarations
handlerdeclarationsprogramcode
END[label];
[label:
]BEGINvaraiableandconditiondeclarationscursordeclarationshandlerdeclarationsprogramcode
END[label];代码块可以嵌套:
Java代码
CREATEPROCEDUREnested_blocks()
BEGIN
DECLAREmy_variablevarchar(20);
SETmy_variable='Thisvaluewassetintheouter
block';
SETmy_variable='Thisvaluewassetintheinner
block';
END;
SELECTmy_variable,'Changesintheinnerblockare
visibleintheouterblock';
END;
CREATEPROCEDUREnested_blocks()
BEGIN
DECLAREmy_variablevarchar(20);
SETmy_variable='Thisvaluewassetintheouterblock';
BEGIN
SETmy_variable='Thisvaluewassetintheinnerblock';
END;
SELECTmy_variable,'Changesintheinnerblockarevisibleintheouterblock';
END;LEAVE的例子:
Java代码
CREATEPROCEDUREnested_blocks()
DECLAREl_statusint;
SETl_status=1;
inner_block:
BEGIN
IF(l_status=1)THEN
LEAVEinner_block;
ENDIF;
SELECT'Thisstatementwillneverbeexecuted';
ENDinner_block;
SELECT'Endofprogram';
ENDouter_block;
CREATEPROCEDUREnested_blocks()outer_block:
BEGIN
DECLAREl_statusint;
SETl_status=1;
inner_block:
BEGIN
IF(l_status=1)THEN
LEAVEinner_block;
ENDIF;
SELECT'Thisstatementwillneverbeexecuted';
ENDinner_block;
SELECT'Endofprogram';
ENDouter_block;2,条件控制
IF:
Java代码
IFexpressionTHENcommands
[ELSEIFexpressionTHENcommands][ELSEcommands]
ENDIF;
IFexpressionTHENcommands[ELSEIFexpressionTHENcommands][ELSEcommands]
ENDIF;例子:
Java代码
IF(sale_value>200)THEN
/*Freeshipping*/
CALLfree_shipping(sale_id);
IF(customer_status='PLATINUM')THEN
discount*/
ELSEIF(customer_status='GOLD')THEN
CALLapply_discount(sale_id,15);/*15%
discount*/
ELSEIF(customer_status='SILVER')THEN
CALLapply_discount(sale_id,10);/*10%
discount*/
ELSEIF(customer_status='BRONZE')THEN
CALLapply_discount(sale_id,5);/*5%discount*/
ENDIF;
ENDIF;
IF(sale_value>200)THEN
/*Freeshipping*/
CALLfree_shipping(sale_id);
IF(customer_status='PLATINUM')THEN
CALLapply_discount(sale_id,20);/*20%discount*/
ELSEIF(customer_status='GOLD')THEN
CALLapply_discount(sale_id,15);/*15%discount*/
ELSEIF(customer_status='SILVER')THEN
CALLapply_discount(sale_id,10);/*10%discount*/
ELSEIF(customer_status='BRONZE')THEN
ENDIF;
ENDIF;CASE:
Java代码
CASE
WHENconditionTHEN
statements
[WHENconditionTHEN
statements...]
[ELSE
statements]
ENDCASE;
CASE
WHENconditionTHENstatements[WHENconditionTHENstatements...][ELSEstatements]
ENDCASE;例子:
Java代码
CASE
WHEN(sale_value>200)THEN
CALLfree_shipping(sale_id);
CASEcustomer_status
WHEN'PLATINUM'THEN
CALLapply_discount(sale_id,20);
WHEN'GOLD'THEN
CALLapply_discount(sale_id,15);
WHEN'SILVER'THEN
CALLapply_discount(sale_id,10);
WHEN'BRONZE'THEN
CALLapply_discount(sale_id,5);
ENDCASE;
ENDCASE;
CASE
WHEN(sale_value>200)THEN
CASEcustomer_status
WHEN'PLATINUM'THEN
CALLapply_discount(sale_id,20);
WHEN'GOLD'THEN
CALLapply_discount(sale_id,15);
WHEN'SILVER'THEN
CALLapply_discount(sale_id,10);
WHEN'BRONZE'THEN
CALLapply_discount(sale_id,5);
ENDCASE;
ENDCASE;CASE与SELECT语句结合的妙用:
Java代码
SELECT(CASEWHEN(t.a=1ANDt.b=0)THENt.c
ELSE'N/A'END)ASresultFROMtesttorderbyresultasc
SELECT(CASEWHEN(t.a=1ANDt.b=0)THENt.c
ELSE'N/A'END)ASresultFROMtesttorderbyresultasc3,迭代
LOOPJava代码
[label:
]LOOP
ENDLOOP[label];
[label:
]LOOPstatements
ENDLOOP[label];REPEAT...UNTILJava代码
[label:
]REPEAT
statements
UNTILexpression
ENDREPEAT[label]
[label:
]REPEATstatements
UNTILexpression
ENDREPEAT[label]WHILEJava代码
[label:
]WHILEexpressionDO
ENDWHILE[label]
[label:
]WHILEexpressionDOstatements
ENDWHILE[label]LEAVE语句Java代码
SETi=1;
myloop:
LOOP
SETi=i+1;
IFi=10then
LEAVEmyloop;
ENDIF:
ENDLOOPmyloop;
SELECT'Icancountto10';
SETi=1;
myloop:
LOOP
SETi=i+1;
IFi=10then
LEAVEmyloop;
ENDIF:
语句Java代码
ENDLOOPmyloop;
SELECT'Icancountto10';ITERATE
SETi=0;
loop1:
LOOP
SETi=i+1;
exitloop*/
LEAVEloop1;
tryagain*/
ITERATEloop1;
ENDIF;
SELECTCONCAT(i,"isanoddnumber");
ENDLOOPloop1;
SETi=0;
loop1:
LOOP
SETi=i+1;
loop*/
LEAVEloop1;
again*/
ITERATEloop1;
ENDIF;
SELECTCONCAT(i,"isanoddnumber");
ENDLOOPloop1;嵌套循环Java代码
DECLAREi,jINTDEFAULT1;
outer_loop:
LOOP
SETj=1;
inner_loop:
LOOP
SELECTconcat(i,"times",j,"is",i*j);
SETj=j+1;
IFj>12THEN
LEAVEinner_loop;
ENDIF;
ENDLOOPinner_loop;
SETi=i+1;
IFi>12THEN
LEAVEouter_loop;
ENDIF;
ENDLOOPouter_loop;
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- 关 键 词:
- mysql 存储 过程 代码 条件 控制