As PostgreSQL connector I import following package:
_ "github.com/lib/pq"
The query I run is:
res, err := db.Query("SELECT id FROM applications WHERE email='" + email + "'")
where email is naturally a string. One way to count the number of rows in res is by following snippet
count:=0
for res.Next() {
count++
//some other code
}
but there should be some simpler (and quicker) way. It seems RowsAffected() is not the way to go. So, what is your suggestion?
Use the COUNT function:
"SELECT count(*) FROM applications WHERE email='" + email + "'"
Related
I am trying to find multiple users based on their name. I am using gorm as follow:
err := db.Where("username IN ?", []string{"name1", "name2"}).Find(&users).Error
But the generated query is:
SELECT * FROM "users_customer"."user" WHERE (username IN 'name1','name2')
when the correct query should be:
SELECT * FROM "users_customer"."user" WHERE username IN ('name1','name2')
So the error pq: syntax error at or near "$1" is thrown. I use the same syntax as stated in the doc, which is db.Where("name IN ?", []string{"jinzhu", "jinzhu 2"}).Find(&users) but don't know why in my case it doesn't work.
Gorm by default ad ' this at each side and it does not add brackets ().
You should add it manually like this :
names := []string{"name1", "name2"}
commaSep := "'" + strings.Join(names, "', '") + "'"
err := db.Where("username IN (?)", commaSep).Find(&users).Error
You can run it here : https://go.dev/play/p/ox3H2gL1yek
OR
err := db.Where("username IN (?)", []string{"name1", "name2"}).Find(&users).Error
I have a simple select statement:
Select * FROM X where X.name in ("bob", "joe") and X.phone='123'
That works fine in postgres,
In my Go code I have the following code:
var phone string = "123"
var names []string = []string{"bob", "joe"}
sqlStatement := `Select * FROM X where X.name in ($1) and X.phone=$2`
rows, sqlerr := db.Query(sqlStatement, names, phone)
but for some reason I error out from that sql.
unsupported Scan, storing driver.Value type into type *string
how can i use my names array in side the sqlstatement?
note: if i do a fmt.printf and paste the sql statement into postgres, i do get data back + if i take out the $1, and manually input the strings
Copying and pasting fragments from some working Go PostgreSQL code:
import (
"database/sql"
"github.com/lib/pq"
)
query := `
. . .
WHERE code = ANY($1)
. . .
`
codes := []string{"JFK", "LGA", "EWR"}
rows, err := db.Query(query, pq.Array(codes))
I solved this using http://jmoiron.github.io/sqlx/#inQueries
var phone string = "123"
var names []string = []string{"bob", "joe"}
sqlStatement := `Select * FROM X where X.name in (?) and X.phone=?`
sqlStatement, args, err := sqlx.In(sqlStatement, names, phone)
sqlStatement = db.Rebind(sqlStatement)
rows, sqlerr := db.Queryx(sqlStatement, args...)
this now returns correctly.
another way to solve this was to use fmt.Sprintf() and converting the ? to %s
I am confused by DISTINCT in JPQL. I have two JPQL queries identical except for "DISTINCT" in one of them:
String getObjectsForFlow =
"SELECT " +
" se.componentID " +
"FROM " +
" StatisticsEvent se " +
"WHERE " +
" se.serverID IS NOT NULL " +
" AND se.flowID = :uuid " +
" AND se.componentID IS NOT NULL " +
"ORDER BY " +
" se.timeStamp desc ";
String getObjectsForFlowDistinct =
"SELECT DISTINCT " +
" se.componentID " +
"FROM " +
" StatisticsEvent se " +
"WHERE " +
" se.serverID IS NOT NULL " +
" AND se.flowID = :uuid " +
" AND se.componentID IS NOT NULL " +
"ORDER BY " +
" se.timeStamp desc ";
I run a little code to get the results from each query and dump them to stdout, and I get many rows with some duplicates for non-distinct, but for distinct I get only one row which is part of the non-distinct list.
NOT DISTINCT
::: 01e2e915-35c1-6cf0-9d0e-14109fdb7235
::: 01e2e915-35c1-6cf0-9d0e-14109fdb7235
::: 01e2e915-35d9-afe0-9d0e-14109fdb7235
::: 01e2e915-35d9-afe0-9d0e-14109fdb7235
::: 01e2e915-35bd-c370-9d0e-14109fdb7235
::: 01e2e915-35bd-c370-9d0e-14109fdb7235
::: 01e2e915-35aa-1460-9d0e-14109fdb7235
::: 01e2e915-35d1-2460-9d0e-14109fdb7235
::: 01e2e915-35e1-7810-9d0e-14109fdb7235
::: 01e2e915-35e1-7810-9d0e-14109fdb7235
::: 01e2e915-35d0-12f0-9d0e-14109fdb7235
::: 01e2e915-35b0-cb20-9d0e-14109fdb7235
::: 01e2e915-35a8-66b0-9d0e-14109fdb7235
::: 01e2e915-35a8-66b0-9d0e-14109fdb7235
::: 01e2e915-35e2-6270-9d0e-14109fdb7235
::: 01e2e915-357f-33d0-9d0e-14109fdb7235
DISTINCT
::: 01e2e915-35e2-6270-9d0e-14109fdb7235
Where are the other entries? I would expect a DISTINCT list containing eleven (I think) entries.
Double check equals() method on your StatisticsEvent entity class. Maybe those semantically different values returns same when equals() is called hence producing this behavior
The problem was the "ORDER BY se.timeStamp" clause. To fulfill the request, JPQL added the ORDER BY field to the SELECT DISTINCT clause.
This is like a border case in the interplay between JPQL and SQL. The JPQL syntax clearly applies the DISTINCT modifier only to se.componentID, but when translated into SQL the ORDER BY field gets inserted.
I am surprised that the ORDER BY field had to be selected at all. Some databases can return a data set ORDERed by a field not in the SELECTion. Oracle can do so. My underlying database is Derby -- could this be a limitation in Derby?
Oracle does not support SELECT DISTINCT with an order by unless the order by columns are in the SELECT. Not sure if any databases do. It will work in Oracle if the DISTINCT is not required (does not run because rows are unique), but if it needs to run you will get an error.
You will get, "ORA-01791: not a SELECTed expression"
If you are using EclipseLink this functionality is controlled by the DatabasPlatform method,
shouldSelectDistinctIncludeOrderBy()
You can extend your platform to return false if your database does not require this.
Still, I don't see how adding the TIMESTAMP will change the query results?
Both queries are incorrect JPQL queries, because ORDER BY clause refers to the item that is not on select list. JPA 2.0 specification contains example that matches to this case:
The following two queries are not legal because the orderby_item is
not reflected in the SELECT clause of the query.
SELECT p.product_name
FROM Order o JOIN o.lineItems l JOIN l.product p JOIN o.customer c
WHERE c.lastname = ‘Smith’ AND c.firstname = ‘John’
ORDER BY p.price
SELECT p.product_name
FROM Order o, IN(o.lineItems) l JOIN o.customer c
WHERE c.lastname = ‘Smith’ AND c.firstname = ‘John’
ORDER BY
o.quantity
Of course it would be nicer if if implementation could give clear error message instead of trying to guess what is expected result of incorrect query.
I'm trying to do an insert or update in a postgres database using node.js with pg extension (version 0.5.4).
So far I have this code:
(...)
client.query({
text: "update users set is_active = 0, ip = $1 where id=$2",
values: [ip,id]
}, function(u_err, u_result){
debug(socket_id,"update query result: ",u_result);
debug(socket_id,"update query error: ",u_err);
date_now = new Date();
var month = date_now.getMonth() + 1;
if(!u_err){
client.query({
text: 'insert into users (id,first_name,last_name,is_active,ip,date_joined) values' +
'($1,$2,$3,$4,$5,$6)',
values: [
result.id,
result.first_name,
result.last_name,
1,
ip,
date_now.getFullYear() + "-" + month + "-" + date_now.getDate() + " " + date_now.getHours() + ":" + date_now.getMinutes() + ":" + date_now.getSeconds()
]
}, function(i_err, i_result){
debug(socket_id,"insert query result: ",i_result);
debug(socket_id,"insert query error: ",i_err);
});
}
});
The problem is that, although both queries work the problem is always running both instead of only running the insert function if the update fails.
The debug functions in code output something like:
UPDATE
Object { type="update query result: ", debug_value={...}}
home (linha 56)
Object { type="update query error: ", debug_value=null}
home (linha 56)
Object { type="insert query result: "}
home (linha 56)
Object { type="insert query error: ", debug_value={...}}
Insert
Object { type="update query result: ", debug_value={...}}
home (linha 56)
Object { type="update query error: ", debug_value=null}
home (linha 56)
Object { type="insert query result: ", debug_value={...}}
home (linha 56)
Object { type="insert query error: ", debug_value=null}
** EDIT **
ANSWER FROM node-postgres developer:
It's possible to retrieve number of rows affected by an insert and
update. It's not fully implemented in the native bindings, but does
work in the pure javascript version. I'll work on this within the
next week or two. In the mean time use pure javascript version and
have a look here:
https://github.com/brianc/node-postgres/blob/master/test/integration/client/result-metadata-tests.js
** END EDIT **
Can anyone help?
The immediate answer to your question is to use a stored procedure to do an upsert.
http://www.postgresql.org/docs/current/static/plpgsql-control-structures.html#PLPGSQL-UPSERT-EXAMPLE
Something like this works fine with the pg module.
client.query({
text: "SELECT upsert($1, $2, $3, $4, $5, $6)"
values: [ obj.id,
obj.first_name,
obj.last_name,
1,
ip,
date_now.getFullYear() + "-" + month + "-" + date_now.getDate() + " " + date_now.getHours() + ":" + date_now.getMinutes() + ":" + date_now.getSeconds()
]
}, function(u_err, u_result){
if(err) // this is a real error, handle it
// otherwise your data is updated or inserted properly
});
Of course this assumes that you're using some kind of model object that has all the values you need, even if they aren't changing. You have to pass them all into the upsert. If you're stuck doing it the way you've shown here, you should probably check the actual error object after the update to determine if it failed because the row is already there, or for some other reason (which is real db error that needs to be handled).
Then you've gotta deal with the potential race condition between the time your update failed and the time your insert goes through. If some other function tries to insert with the same id, you've got a problem. Transactions are good for that. That's all I got right now. Hope it helps.
I had this issue when connecting to a PG instance using the JDBC. The solution I ended up using was:
UPDATE table SET field='C', field2='Z' WHERE id=3;
INSERT INTO table (id, field, field2)
SELECT 3, 'C', 'Z'
WHERE NOT EXISTS (SELECT 1 FROM table WHERE id=3);
The update does nothing if the record doesn't exist and the insert does nothing if the record does exist. It works pretty well and is an SQL based solution vs a stored procedure.
Here's the initial question:
Insert, on duplicate update in PostgreSQL?
I have an electronic component database to which I add components that I either salvage from e-waste or buy as new, and the way I did it was:
const upsertData = (request, response) => {
const {
category, type, value, unit, qty,
} = request.body;
pool.query(`DO $$
BEGIN
IF EXISTS
( SELECT 1
FROM elab
WHERE category='${category}'
AND type='${type}'
AND value='${value}'
AND unit='${unit}'
)
THEN
UPDATE elab
SET qty = qty + ${qty}
WHERE category='${category}'
AND type='${type}'
AND value='${value}'
AND unit='${unit}';
ELSE
INSERT INTO elab
(category, type, value, unit, qty)
values ('${category}', '${type}', '${value}', '${unit}', ${qty});
END IF ;
END
$$ ;`, (error, results) => {
if (error) {
throw error;
}
response.status(201).send('Task completed lol');
});
};
The reason for this was that the only unique column any entry had was the ID, which is automatically updated, none of the other columns are unique only the whole entry is e.g. you can have a 100 kOhm resistor as a potentiometer or a "normal" one - and you can have a potentiometer with different values than 100 kOhm so only the whole entry is unique.
Tutorials and samples about JPQL always deal with SELECT statement and sometimes, simple UPDATE statements. I need to update a table with a join.
I have simplified my env :
KEY
= id
- counter
APPLET
= id
! key_id (1-1)
DEVICE
= id
! applet_id (1-1)
! user_id (1-n)
USER
= id
- login
A device has a unique applet, which has a unique keyset. But an user can own several devices.
I need to reset the counter of every KEY attached to the USER login "x".
I tried some syntax with UPDATE and JOIN, without success. Any clue ?
Thank you.
What did you try and what error did you get? What is your object model?
Perhaps something like,
Update Key k set k.counter = 0 where exists (Select u from User u join u.devices d where u.login = "x" and d.applet.key = k)
See,
http://en.wikibooks.org/wiki/Java_Persistence/JPQL_BNF#Update
You could also select the objects and reset the counter in memory and commit the changes.
JPQL does not support join operations in bulk update operations.
When you edit query, nativeQuery = true, you can join.
Query should be written according to the fields in the database.
#Transactional
#Modifying
#Query(nativeQuery = true,
value = "UPDATE Team t" +
" SET current = :current " +
" FROM " +
" members," +
" account" +
" WHERE " +
" members.members_id = t.members_id " +
" AND members.account_id = :account " +
" AND t.current = :current_true ")
int updateTeam(
#Param("current") String current,
#Param("account") Long account,
#Param("current_true") Integer current_true);