Develop Reference

Insert into SQLite database if not exist in Java [duplicate]

I have an SQLite database. I am trying to insert values (users_id, lessoninfo_id) in table bookmarks, only if both do not exist before in a row.
INSERT INTO bookmarks(users_id,lessoninfo_id)
VALUES(
(SELECT _id FROM Users WHERE User='"+$('#user_lesson').html()+"'),
(SELECT _id FROM lessoninfo
WHERE Lesson="+lesson_no+" AND cast(starttime AS int)="+Math.floor(result_set.rows.item(markerCount-1).starttime)+")
WHERE NOT EXISTS (
SELECT users_id,lessoninfo_id from bookmarks
WHERE users_id=(SELECT _id FROM Users
WHERE User='"+$('#user_lesson').html()+"') AND lessoninfo_id=(
SELECT _id FROM lessoninfo
WHERE Lesson="+lesson_no+")))
This gives an error saying:
db error near where syntax.

If you never want to have duplicates, you should declare this as a table constraint:
CREATE TABLE bookmarks(
users_id INTEGER,
lessoninfo_id INTEGER,
UNIQUE(users_id, lessoninfo_id)
);
(A primary key over both columns would have the same effect.)
It is then possible to tell the database that you want to silently ignore records that would violate such a constraint:
INSERT OR IGNORE INTO bookmarks(users_id, lessoninfo_id) VALUES(123, 456)

If you have a table called memos that has two columns id and text you should be able to do like this:
INSERT INTO memos(id,text)
SELECT 5, 'text to insert'
WHERE NOT EXISTS(SELECT 1 FROM memos WHERE id = 5 AND text = 'text to insert');
If a record already contains a row where text is equal to 'text to insert' and id is equal to 5, then the insert operation will be ignored.
I don't know if this will work for your particular query, but perhaps it give you a hint on how to proceed.
I would advice that you instead design your table so that no duplicates are allowed as explained in #CLs answer below.

For a unique column, use this:
INSERT OR REPLACE INTO tableName (...) values(...);
For more information, see: sqlite.org/lang_insert

insert into bookmarks (users_id, lessoninfo_id)
select 1, 167
EXCEPT
select user_id, lessoninfo_id
from bookmarks
where user_id=1
and lessoninfo_id=167;
This is the fastest way.
For some other SQL engines, you can use a Dummy table containing 1 record.
e.g:
select 1, 167 from ONE_RECORD_DUMMY_TABLE

Merge and When Matched query giving an error sql server

I have a query which I am trying to test. The query should update the data if it finds data in the table with existing primary key. If it doesn't then insert into the table.
The Primary key is of type int and in the properties I can see Identity is set to "True" which I assume it means that it will automatically set the new id for the primary if it is inserted.
MERGE INTO Test_table t
USING (SELECT 461232 ID,'Test1-data' Fascia FROM Test_table) s
ON (t.ID = s.ID)
WHEN MATCHED THEN
UPDATE SET t.Fascia = s.Fascia
WHEN NOT MATCHED THEN
INSERT (Fascia)
VALUES (s.Fascia);
The issue here is this query doesn't work and it never inserts the data or updates. Also, query gets compiled and I don't get any compilation error
Also the reason I want this query is to work because then I will use Java prepared statement to query the database so I am assuming I can do
SELECT ? ID,? Fascia FROM Test_table
So that I can pass the values with set methods in java.
Please let me know if there is something wrong in my query.

You are selecting from the target table as your source.
You either need to remove your FROM Test_table or have at least 1 row in Test_table prior to your merge.
rextester demo: http://rextester.com/XROJD28508
MERGE INTO Test_table t
USING (SELECT 461232 ID,'Test1-data' Fascia --FROM Test_table
) s
ON (t.ID = s.ID)
WHEN MATCHED THEN
UPDATE SET t.Fascia = s.Fascia
WHEN NOT MATCHED THEN
INSERT (Fascia)
VALUES (s.Fascia);

HQL : The column must appear in GROUP BY or in Select

I've this query with WrappedBean :
buffer.append("SELECT new myPackage.WrappedBean(E.debitant.id, E.dateCalcul, E.verse, E.incidenceReprise, E.soldeSoumission) ");
buffer.append("FROM " + getEntityClassName() + " E ");
buffer.append("LEFT JOIN E.debitant DT ");
buffer.append("WHERE E.debitant.id = :idDebitant ");
buffer.append("AND YEAR(E.dateCalcul) = :year ");
buffer.append("GROUP BY E.debitant.id");
hqlQuery = session.createQuery(buffer.toString());
hqlQuery.setInteger("idDebitant", idDebitant);
hqlQuery.setInteger("year", year);
I've created WrappedBean for returning somme columns and for using Group BY.
When i try to execute it, i obtain this error :
org.postgresql.util.PSQLException: ERREUR: The column « complement0_.date_calcul » must appear in GROUP BY clause or must be used in Select (i translate the error from french)
My POSTGRES query doesnt contain date_calcul in Group BY.
Another problem, in my query i've also this :
SUM(CASE WHEN YEAR(dateCalcul)=#PECAnnee AND verse>0 THEN verse ELSE 0 END)
I know in HQL, we cant do case when in select, for this reason, i dont add SUM to column verse
What i've forgot ?

My POSTGRES query doesnt contain date_calcul in Group BY
That's the problem and what Postgres is complaining about. Why isn't it in the SQL query? Because it isn't in the HQL query. Any column that is selected without the use of some aggregate method like sum(), min(), max() etc. needs to be part of the GROUP BY clause since otherwise the DB doesn't know how to handle multiple values/conflicts.
As an example, what value of E.dateCalcul should be passed to WrappedBean if there are multiple debitors (debitants) (which is most probably the case since otherwise there wouldn't be any need for the GROUP BY clause)?
So to fix this either use
GROUP BY E.debitant.id, E.dateCalcul, E.verse, E.incidenceReprise, E.soldeSoumission
or use aggregate functions, e.g.
WrappedBean(E.debitant.id, max(E.dateCalcul), min(E.verse), max(E.incidenceReprise), sum(E.soldeSoumission))

Java Regex: To know the number of rows to be returned by a SQL Query

I have a SQL query and I want to know how many rows will that SQL query return. Now the problem is that I want to know the number of results beforehand which means before running the SQL query.
I would have done this easily by ResultSet.getRow() to get the total number of rows from resultset. But as per the requirement, I can get the resultset only after knowing the number of rows to be returned by that query.
I tried the below Java Regex to solve the issue:
String orgQuery = "select * from emp where id<1210 and salary>55000;"
Pattern p= Pattern.compile("(?:)from\\s+(.*)*" , Pattern.CASE_INSENSITIVE);
Matcher m= p.matcher(orgQuery);
if (m.find()) {
countQuery = "SELECT COUNT(*) as total "+ m.group(1);
System.out.println(countQuery);
}
This work perfectly file and I get the "countQuery" as:
SELECT COUNT(*) as total from emp where id<1210 and salary>55000
By this I can easily know the number of rows to be returned beforehand but the problem occurs when my query become more complex like these two:--
even more complex in case of nested queries i.e. #query2.
#query1: select * from emp where id<1210 and salary>55000 order by dept, salary desc;
#query2: select name from emp where id IN (select id from emp where id < 1210 group by salary , id order by id ASC limit 10) order by id DESC limit 10
I think the main issue is with "Order By" clause. I can remove the "Order By" clause too by below regex:
Pattern.compile("(?:)from\\s+(.*)*" , Pattern.CASE_INSENSITIVE);
But it becomes more complex in case of Nested queries.
Can any Java Regex expert help????? I am using postgres as DB.

Wrap your existing query like so:
select count(*) from (<existing query>)
With your given example:
String orgQuery = "select * from emp where id<1210 and salary>55000";
String countQuery = "select count (*) from (" + orgQuery + ')';
I know this works with Oracle. I have not used postgres, so I am not certain if there would be anything preventing this approach from working there.
I will caution on this idea of getting a count first, however, that it might be possible for the data to change between your execution of the count and the actual query.

Detect, delete empty columns and update database in sql, oracle

I have 100 of columns and some of the doesn't have any values inside(they are empty) how can I search for empty columns and delete from table and update database? I tried this query but it doesnt work. It shows 0 rows selected. After selecting how can I update the database?
select table_name, column_name
from all_tab_columns
where table_name='some_table'
and column_name is NULL;
Thanks,

You are querying a data dictionary view. It shows meta-data, in formation about the database. This view, ALL_TAB_COLUMNS, shows information for every column of every table (you have privileges on). Necessarily COLUMN_NAME cannot be null, hence your query returns no rows.
Now what you want to do is query every table and find which columns have no data in them. This requires dynamic SQL. You will need to query ALL_TAB_COLUMNS, so you weren't completely off-base.
Because of dynamic SQL this is a programmatic solution, so the results are displayed with DBMS_OUTPUT.
set serveroutput on size unlimited
Here is an anonymous block: it might take some time to run. The join to USER_TABLES is necessary because columns from views are included in TAB_COLUMNS and we don't want those in the result set.
declare
dsp varchar2(32767);
stmt varchar2(32767);
begin
<< tab_loop >>
for trec in ( select t.table_name
from user_tables t )
loop
stmt := 'select ';
dbms_output.put_line('table name = '|| trec.table_name);
<< col_loop >>
for crec in ( select c.column_name
, row_number() over (order by c.column_id) as rn
from user_tab_columns c
where c.table_name = trec.table_name
and c.nullable = 'Y'
order by c.column_id )
loop
if rn > 1 then stmt := concat(stmt, '||'); end if;
stmt := stmt||''''||crec.column_name||'=''||'
||'to_char(count('||crec.column_name||')) ';
end loop col_loop;
stmt := stmt || ' from '||trec.table_name;
execute immediate stmt into dsp;
dbms_output.put_line(dsp);
end loop tab_loop;
end;
sample output:
table name = MY_PROFILER_RUN_EVENTS
TOT_EXECS=0TOT_TIME=0MIN_TIME=0MAX_TIME=0
table name = LOG_TABLE
PKG_NAME=0MODULE_NAME=0CLIENT_ID=0
PL/SQL procedure successfully completed.
SQL>
Any column where the COUNT=0 has no values in it.
Now whether you actually want to drop such columns is a different matter. You might break programs which depend on them. So you need an impact analysis first. This is why I have not produced a program which automatically drops the empty columns. I think that would be dangerous practice.
It is crucial that changes to our database structure are considered and audited. So if I were ever to undertake an exercise like this I would alter the output from the program above so it produced a script of drop column statements which I could review, edit and keep under source control.