Assume I have a db table with two columns: first_name and last_name with 50 rows and I have created all the mappings in MyBatis
#Select("SELECT * FROM users")
#Results({
#Result(property = "firstName", column = "first_name"),
#Result(property = "lastName", column = "last_name")
})
List<User> findUsers();
Now, if I want to get the 5th name from the first_name column, how do I iterate the List and get that.
Thank you in advance for any help.
Well, once you have the list of user it is easy.
List<User> users = myService.findUsers();
String my5thName = users.get(4).getFirstName();
Did I understand well your question?
Related
I have following query which select from employee table where name is "max" and ID not in 123 and 444.
Not in IDs can grow in future. But I am receiving error as
Error
( 8023): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: DatabaseException(near "?": syntax error (code 1 SQLITE_ERROR): , while compiling:
Query
List<String> a = [];
a.add("123");
a.add("444");
var table = await mydb.rawQuery(
"SELECT value from employee WHERE employeename = ? AND id NOT IN ? ORDER BY timestamp DESC",
["max", a]);
If the LIST is unpredictable, one way is that you can use JOIN to create your select statement with required value of NOT IN. Below is one sample.
void main() {
List<String> a = [];
a.add("123");
a.add("444");
var select =
'SELECT value from employee WHERE employeename = ? AND id NOT IN (\'' +
(a.join('\',\'')).toString() +
'\') ORDER BY timestamp DESC';
var table = await mydb.rawQuery(select, ["max"]);
}
If you print the variable select you will get
SELECT value from employee WHERE employeename = ? AND id NOT IN ('123','444')
ORDER BY timestamp DESC.
Then you can pass the above statement to rawquery and get your result.
P.S:Use your single quote and double quote accordingly.
I'd go for #arun-palanisamy 's solution, see his comment. Props go to him. I just tried the following -- with Groovy/Postgres, but the error seems to be the same, so you might want to give it a try:
String[] a = ['123', '444']
// your code, throws 'ERROR: syntax error at or near "$2"':
// def table = sql.execute("SELECT value from employee WHERE employeename = ? AND id NOT IN ? ORDER BY timestamp DESC", ["max", a])
// code of arun-palanisamy, compiles:
def table = sql.execute("SELECT value from employee WHERE employeename = ? AND id NOT IN (${a.join(', ')}) ORDER BY timestamp DESC", ["max", a])
Side notes:
You might want to try a different type for a, such as Array in my code, or even a HashMap.
There are examples (like here) where the number of ? are generated dynamically.
Update: Go for this answer, we posted simultaneously
I use JPA 2.0 criteria builder. I need get data from one table and sort them by column from other. This tables have relations OneToMany:
class Club{
#OneToMany(mappedBy = "club")
private List<Address> addresses;
...
}
class Address{
#JoinColumn(name = "club_id", referencedColumnName = "id")
#ManyToOne(fetch = FetchType.LAZY)
private Club club;
#Column(name = "type")
private Long type;
#Column(name = "full_address")
private String full_address;
...
}
May be several address of some type but I need only one row of this specific address.
I write native queries with subquery, but it's has problem because subquery doesn't use in order clause and in select clause in JPA 2.0.
select c.full_name from club c
ORDER BY (select a.full_address from address a WHERE c.id= a.club_id and a.type=1 LIMIT 1)
select c.full_name, (select a.full_address from address a WHERE a.type=1 AND c.id=a.club_id LIMIT 1) as full_address FROM club c
ORDER BY fullAddress;
How I can replace native order by clause on JPA equivalent?
Thanks!
This native query also resolve problem and it can replace by JPA query
select c.full_name, min(a.full_address) FROM club c LEFT JOIN address a on c.id = a.club_id
where a.id is null or a.type=1 or not exists(SELECT 1 from address aSub WHERE aSub .club_id=c.id AND aSub.type=1)
GROUP BY c.id, c.full_name ORDER BY min(a.full_address);
JPA equivalent
CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaQuery<ClubItem> query = builder.createQuery(ClubItem.class);
Root<Club> root = query.from(Club.class);
Join<Club, Address> addressJoin = root.join(Club_.address, JoinType.LEFT);
query.select(builder.construct(ClubItem.class, root.get(Club_.id), root.get(Club_.fullName), builder.function("min", String.class, addressJoin.get(Address_.fullAddress))));
Subquery<Address> subquery = query.subquery(Address.class);
Root<Address> addressRoot = subquery.from(Address.class);
subquery.select(addressRoot);
subquery.where(
builder.and(
builder.equal(addressRoot.get(Address_.type), 1),
builder.equal(addressRoot.get(Address_.clubId), root.get(Club_.id))));
query.where(builder.or(builder.isNull(addressJoin), builder.equal(addressJoin.get(Address_.type), builder.literal(new Long(1))),
builder.not(builder.exists(subquery))));
query.groupBy(root.get(Club_.id), root.get(Club_.fullName))
Order order = builder.asc(builder.function("min", String.class, addressJoin.get(Address_.fullAddress)));
query.orderBy(order);
TypedQuery<ClubItem> contentQuery = em.createQuery(query);
It's not terribly elegant, but it gets the job done...
Make your "Club" class implement Comparable. Put the order-by logic into the Comparable. Then use Collections.sort(unsortedList) to get the list into sorted form. There's also a Collections.sort(unsortedList, Comparable) method which could be useful, especially if you are doing a bunch of similar methods that just vary on order-by.
I have a table patient_details(patient_id, first_name, last_name, address,date_of_birth, gender, contact_number,occupation). I have generated an entity class and a PersistenceUnit. I can only find an object using its ID:
PatientDetails pd = em.find(PatientDetails.class,patient_id);
I want to know how to find an object by using other column name(s) instead of just the primary key.
Have a look on JPQL or JPA Critera.
https://docs.oracle.com/html/E24396_01/ejb3_langref.html
http://docs.oracle.com/javaee/6/tutorial/doc/gjitv.html
Execute Querys:
http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html#createQuery%28javax.persistence.criteria.CriteriaQuery%29
For example:
if
class PatientDetails
String first_name;
#Column(",date_of_birth")
Date birth;
...
}
then
String sql = "SELECT p FROM PatientDetails p where p.first_name = :fname and p.birth > :generation";
Date generation = new Date(int 1980, 0, 1);
TypedQuery<PatientDetails> query = EM.createQuery(sql);
query.setParameter("fname","John");
query.setParameter("generation",generation);
return query.getResultList
returns patients called John and born after 1980.
But you should read the links recommended by #pL4Gu33
I have a problem in JPQL cascade query with eclipselink2.5
please see code
Entity code
public class Category{
...
#JoinColumn(name = "parent_category", referencedColumnName = "id")
#ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER,optional = true)
private Category parentCategory;
...
}
JPQL code
String jpql = "select o from Category o order by o.parentCategory.sort ASC";
problem
the problem is this JPQL return list does not include 'o' if 'o.parentCategory' is null.
please see this table http://i.stack.imgur.com/xsXvk.jpg
the return list only rows id is 2,3,4 .
because the column parent_category is null, I lost rows 1,5,6
the correct result should be return all rows
Looking forward to your help！
Using o.parentCategory.sort in the order by clause forces an inner join which filters nulls. If you want nulls included, you will need to use an explicit outer join in the query:
"select o from Category o outer join o.parentCategory parentCategory order by parentCategory.sort ASC"
I have the following QueryDSL query:
QCustomer customer = QCustomer.customer;
BooleanBuilder builder = new BooleanBuilder();
builder.or(customer.person.name.containsIgnoreCase(query));
builder.or(customer.company.name.containsIgnoreCase(query));
return builder;
And I expect to get results from Persons that contains the name = query and/or Companies that contains the query parameter. But I get nothing.
This is my Customer class mapping:
#OneToOne(orphanRemoval = false, optional = true, cascade = CascadeType.ALL)
private Company company;
#OneToOne(orphanRemoval = false, optional = true, cascade = CascadeType.ALL)
private Person person;
Did someone knows what I'm missing here?
I expect to get a query like this:
select o
from Customer
where o.person.name like '%:name%' or o.company.name like '%:name%'
This is the generated query:
select
count(customer0_.uid) as col_0_0_
from
Customer customer0_
cross join
Person person1_
cross join
Company company2_
where
customer0_.person_uid=person1_.uid
and customer0_.company_uid = company2_.uid
and (lower(person1_.name) like ? escape '!' or lower(company2_.name) like ? escape '!') limit ?
It uses a count because it's the first query that Spring Data use to paginate the result.
The query looks ok. Most probably you get wrong results because the implicit property based joins make the joins inner joins.
Using left joins you might get the results you need.
QPerson person = QPerson.person;
QCompany company = QCompany.company;
BooleanBuilder builder = new BooleanBuilder();
builder.or(person.name.containsIgnoreCase(str));
builder.or(company.name.containsIgnoreCase(str));
query.from(customer)
.leftJoin(customer.person, person)
.leftJoin(customer.company, company)
.where(builder);