利用Java理解sql的语法(实例讲解)

利用Java理解sql的语法(实例讲解)

select 相当于 for 循环

select id from IDArray

LinkedList a = new LinkedList();

for ( int i=0 ; i

a.add(IDArray.get("id" ) );

}

return a;

当执行子查询时，可以理解为

select id, ( select name from nameArray) as names ,from Idarray

LinkedList a = new LinkedList();

for ( int i=0 ; i

a.add(IDArray.get("id" ) );

for(int j=0 ; j

a.add(namesArray.get("name"));

}

}

很明显这里一对多了。所以执行不对。报SQL错误

所以在 select中，应该要具体确定某一个值

select id, ( select name from nameArray where nameId=id) as names from Idarray

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArrahttp://y.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

当且仅当if 条件的值搜索是单个值的时候，是对应上的

那么groupBy呢？

select id, ( select nJlBRtMame from nameArrahttp://y where nameId=id) as names from Idarray group by id

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

a.add(IDArray.get("id" ) );

}

return a;

当执行子查询时，可以理解为

select id, ( select name from nameArray) as names ,from Idarray

LinkedList a = new LinkedList();

for ( int i=0 ; i

a.add(IDArray.get("id" ) );

for(int j=0 ; j

a.add(namesArray.get("name"));

}

}

很明显这里一对多了。所以执行不对。报SQL错误

所以在 select中，应该要具体确定某一个值

select id, ( select name from nameArray where nameId=id) as names from Idarray

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArrahttp://y.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

当且仅当if 条件的值搜索是单个值的时候，是对应上的

那么groupBy呢？

select id, ( select nJlBRtMame from nameArrahttp://y where nameId=id) as names from Idarray group by id

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

a.add(IDArray.get("id" ) );

for(int j=0 ; j

a.add(namesArray.get("name"));

}

}

很明显这里一对多了。所以执行不对。报SQL错误

所以在 select中，应该要具体确定某一个值

select id, ( select name from nameArray where nameId=id) as names from Idarray

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArrahttp://y.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

当且仅当if 条件的值搜索是单个值的时候，是对应上的

那么groupBy呢？

select id, ( select nJlBRtMame from nameArrahttp://y where nameId=id) as names from Idarray group by id

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

a.add(namesArray.get("name"));

}

}

很明显这里一对多了。所以执行不对。报SQL错误

所以在 select中，应该要具体确定某一个值

select id, ( select name from nameArray where nameId=id) as names from Idarray

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArrahttp://y.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

当且仅当if 条件的值搜索是单个值的时候，是对应上的

那么groupBy呢？

select id, ( select nJlBRtMame from nameArrahttp://y where nameId=id) as names from Idarray group by id

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArrahttp://y.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

当且仅当if 条件的值搜索是单个值的时候，是对应上的

那么groupBy呢？

select id, ( select nJlBRtMame from nameArrahttp://y where nameId=id) as names from Idarray group by id

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

if ( nameArrahttp://y.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

当且仅当if 条件的值搜索是单个值的时候，是对应上的

那么groupBy呢？

select id, ( select nJlBRtMame from nameArrahttp://y where nameId=id) as names from Idarray group by id

LinkedList a = new LinkedList();

for ( int i=0 ; i

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

Object object = IDArray.get("id" ) ;

for ( int j=0 ; j

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

if ( nameArray.get("nameId")==object){

Object object2 = nameArray.get("nameId");

a.add(object2);

}

}

a.add(object);

}

LinkedList groupByArray = new LinkedList();

for ( int i=0 ; i< a. length ; i++){

int id = a[i].getId();

LinkedList tempArray = new LinkedList();

for ( int j=0 ; j

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

int temp = a[j].getId();

if ( id==temp){

tempArray.add(temp);

}

}

groupByArray.add(tempArray);

}

版权声明：本文内容由网络用户投稿，版权归原作者所有，本站不拥有其著作权，亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容，请联系我们jiasou666@gmail.com 处理，核实后本网站将在24小时内删除侵权内容。