You can do it this way:
UPDATE table_users
SET cod_user = (case when user_role = 'student' then '622057'
when user_role = 'assistant' then '2913659'
when user_role = 'admin' then '6160230'
end),
date = '12082014'
WHERE user_role in ('student', 'assistant', 'admin') AND
cod_office = '17389551';
I don't understand your date format. Dates should be stored in the database using native date and time types.
Answer from Gordon Linoff on Stack OverflowYou can do it this way:
UPDATE table_users
SET cod_user = (case when user_role = 'student' then '622057'
when user_role = 'assistant' then '2913659'
when user_role = 'admin' then '6160230'
end),
date = '12082014'
WHERE user_role in ('student', 'assistant', 'admin') AND
cod_office = '17389551';
I don't understand your date format. Dates should be stored in the database using native date and time types.
MySQL allows a more readable way to combine multiple updates into a single query. This seems to better fit the scenario you describe, is much easier to read, and avoids those difficult-to-untangle multiple conditions.
INSERT INTO table_users (cod_user, date, user_rol, cod_office)
VALUES
('622057', '12082014', 'student', '17389551'),
('2913659', '12082014', 'assistant','17389551'),
('6160230', '12082014', 'admin', '17389551')
ON DUPLICATE KEY UPDATE
cod_user=VALUES(cod_user), date=VALUES(date)
This assumes that the user_rol, cod_office combination is a primary key. If only one of these is the primary key, then add the other field to the UPDATE list.
If neither of them is a primary key (that seems unlikely) then this approach will always create new records - probably not what is wanted.
However, this approach makes prepared statements easier to build and more concise.
mysql - Updating multiple rows with different values in one query - Database Administrators Stack Exchange
sqlite - Update multiple rows with different values in a single SQL query - Stack Overflow
Multiple rows updation in sql server
Update multiple rows with different values in SQL - Stack Overflow
Videos
| Id | Name | Price |
|---|---|---|
| 1 | Pen | 50 |
| 2 | Pencil | 60 |
This is my table structure now I want to update the price of Pen and Pencil at the same time with one SQL query
UPDATE mytable SET
fruit = CASE WHEN id=1 THEN 'orange' ELSE 'strawberry' END,
drink = CASE WHEN id=1 THEN 'water' ELSE 'wine' END,
food = CASE WHEN id=1 THEN 'pizza' ELSE 'fish' END
WHERE id IN (1,2);
Personally, using CASE WHEN THEN END looks clumsy.
You could code this using the IF function.
UPDATE mytable SET
fruit = IF(id=1,'orange','strawberry'),
drink = IF(id=1,'water','wine'),
food = IF(id=1,'pizza','fish')
WHERE id IN (1,2);
Give it a Try !!!
CAVEAT : CASE WHEN THEN END is only handy when dealing with multiple values (more than 2)
INSERT ... ON DUPLICATE KEY UPDATE
You will need to write very complicated conditions if you want to update more than two rows. In such a case you can use INSERT ... ON DUPLICATE KEY UPDATE approach.
INSERT into `mytable` (id, fruit, drink, food)
VALUES
(1, 'orange', 'water', 'pizza'),
(2, 'strawberry', 'wine', 'fish'),
(3, 'peach', 'jiuce', 'cake')
ON DUPLICATE KEY UPDATE
fruit = VALUES(fruit),
drink = VALUES(drink),
food = VALUES(food);
There's a couple of ways to accomplish this decently efficiently.
First -
If possible, you can do some sort of bulk insert to a temporary table. This depends somewhat on your RDBMS/host language, but at worst this can be accomplished with a simple dynamic SQL (using a VALUES() clause), and then a standard update-from-another-table. Most systems provide utilities for bulk load, though
Second -
And this is somewhat RDBMS dependent as well, you could construct a dynamic update statement. In this case, where the VALUES(...) clause inside the CTE has been created on-the-fly:
WITH Tmp(id, px, py) AS (VALUES(id1, newsPosX1, newPosY1),
(id2, newsPosX2, newPosY2),
......................... ,
(idN, newsPosXN, newPosYN))
UPDATE TableToUpdate SET posX = (SELECT px
FROM Tmp
WHERE TableToUpdate.id = Tmp.id),
posY = (SELECT py
FROM Tmp
WHERE TableToUpdate.id = Tmp.id)
WHERE id IN (SELECT id
FROM Tmp)
(According to the documentation, this should be valid SQLite syntax, but I can't get it to work in a fiddle)
One way: SET x=CASE..END (any SQL)
Yes, you can do this, but I doubt that it would improve performances, unless your query has a real large latency.
If the query is indexed on the search value (e.g. if id is the primary key), then locating the desired tuple is very, very fast and after the first query the table will be held in memory.
So, multiple UPDATEs in this case aren't all that bad.
If, on the other hand, the condition requires a full table scan, and even worse, the table's memory impact is significant, then having a single complex query will be better, even if evaluating the UPDATE is more expensive than a simple UPDATE (which gets internally optimized).
In this latter case, you could do:
UPDATE table SET posX=CASE
WHEN id=id[1] THEN posX[1]
WHEN id=id[2] THEN posX[2]
...
ELSE posX END [, posY = CASE ... END]
WHERE id IN (id[1], id[2], id[3]...);
The total cost is given more or less by: NUM_QUERIES * ( COST_QUERY_SETUP + COST_QUERY_PERFORMANCE ). This way, you knock down on NUM_QUERIES (from N separate id's to 1), but COST_QUERY_PERFORMANCE goes up (about 3x in MySQL 5.28; haven't yet tested in MySQL 8).
Otherwise, I'd try with indexing on id, or modifying the architecture.
This is an example with PHP, where I suppose we have a condition that already requires a full table scan, and which I can use as a key:
// Multiple update rules
$updates = [
"fldA='01' AND fldB='X'" => [ 'fldC' => 12, 'fldD' => 15 ],
"fldA='02' AND fldB='X'" => [ 'fldC' => 60, 'fldD' => 15 ],
...
];
The fields updated in the right hand expressions can be one or many, must always be the same (always fldC and fldD in this case). This restriction can be removed, but it would require a modified algorithm.
I can then build the single query through a loop:
$where = [ ];
$set = [ ];
foreach ($updates as $when => $then) {
$where[] = "({$when})";
foreach ($then as $fld => $value) {
if (!array_key_exists($fld, $set)) {
$set[$fld] = [ ];
}
$set[$fld][] = $value;
}
}
$set1 = [ ];
foreach ($set as $fld => $values) {
$set2 = "{$fld} = CASE";
foreach ($values as $i => $value) {
$set2 .= " WHEN {$where[$i]} THEN {$value}";
}
$set2 .= ' END';
$set1[] = $set2;
}
// Single query
$sql = 'UPDATE table SET '
. implode(', ', $set1)
. ' WHERE '
. implode(' OR ', $where);
Another way: ON DUPLICATE KEY UPDATE (MySQL)
In MySQL I think you could do this more easily with a multiple INSERT ON DUPLICATE KEY UPDATE, assuming that id is a primary key keeping in mind that nonexistent conditions ("id = 777" with no 777) will get inserted in the table and maybe cause an error if, for example, other required columns (declared NOT NULL) aren't specified in the query:
INSERT INTO tbl (id, posx, posy, bazinga)
VALUES (id1, posY1, posY1, 'DELETE'),
...
ON DUPLICATE KEY SET posx=VALUES(posx), posy=VALUES(posy);
DELETE FROM tbl WHERE bazinga='DELETE';
The 'bazinga' trick above allows to delete any rows that might have been unwittingly inserted because their id was not present (in other scenarios you might want the inserted rows to stay, though).
For example, a periodic update from a set of gathered sensors, but some sensors might not have been transmitted:
INSERT INTO monitor (id, value)
VALUES (sensor1, value1), (sensor2, 'N/A'), ...
ON DUPLICATE KEY UPDATE value=VALUES(value), reading=NOW();
(This is a contrived case, it would probably be more reasonable to LOCK the table, UPDATE all sensors to N/A and NOW(), then proceed with INSERTing only those values we do have).
A third way: CTE (Any SQL)
This is conceptually almost the same as the INSERT MySQL trick. As written, it works in PostgreSQL 9.6:
WITH updated(id, posX, posY) AS (VALUES
(id1, posX1, posY1),
(id2, posX2, posY2),
...
)
UPDATE myTable
SET
posX = updated.posY,
posY = updated.posY
FROM updated
WHERE (myTable.id = updated.id);
UPDATE T
SET Size = CASE SKU
WHEN 'A' THEN 20
WHEN 'B' THEN 10
WHEN 'C' THEN 30
WHEN ...
END
Or there may be a formula for calculating the size, but you've failed to give it in your question (Or we may have to switch to a more complex CASE expression, but again, too little detail in the question).
Create a table with the mapping of SKU to new size; update the master table from that.
Many dialects of SQL have a notation for doing updates via joined tables. Some do not. This will work where there is no such notation:
CREATE TABLE SKU_Size_Map
(
SKU CHAR(16) NOT NULL,
Size INTEGER NOT NULL
);
...Populate this table with the SKU values to be set...
...You must have such a list...
UPDATE MasterTable
SET Size = (SELECT Size FROM SKU_Size_Map
WHERE MasterTable.SKU = SKU_Size_Map.Size)
WHERE SKU IN (SELECT SKU FROM SKU_Size_Map);
The main WHERE condition is need to avoid setting the size to null where there is no matching row.
You can probably also do it with a MERGE statement. But the key insight for any of these notations is that you need a table to do the mapping between SKU and size. You either need a table or you need an algorithm, and the sample data doesn't suggest an algorithm.
Couldn't find a SQL Server 2008 fiddle engine so I had to opt for a SQL Server 2014 ... so not sure if the following will work in SQL Server 2008, but fwiw ...
Setup some sample data:
create table Table1(id int, Date datetime null);
create table Table2(id int, Date datetime);
insert Table1 values (1,null)
insert Table1 values (1,null)
insert Table1 values (2,null)
insert Table1 values (2,null)
insert Table1 values (2,null);
insert Table2 values (1,'2013-01-29 08:50:00.000')
insert Table2 values (1,'2013-01-29 15:28:00.000')
insert Table2 values (2,'2013-01-31 11:56:00.000')
insert Table2 values (2,'2013-03-11 16:08:00.000')
insert Table2 values (2,'2013-01-31 14:04:00.000');
Keeping in mind that we haven't been provided (yet) with any means to determine which rows to match between Table1 and Table2 for a given id value, I'll just let row_number() generate a 'matching' rowid.
And then we'll make use of SQL Server's ability to update Table1 via a derived table definition:
update T1
set T1.Date=T2.Date
from (select row_number() over(partition by id order by Date) as rowid,
id,
Date
from Table1
where Date is NULL) T1
join (select row_number() over(partition by id order by Date) as rowid,
id,
Date
from Table2) T2
on T1.id = T2.id
and T1.rowid = T2.rowid;
And the results:
select * from Table1;
id Date
--- --------------------
1 2013-01-29T08:50:00Z
1 2013-01-29T15:28:00Z
2 2013-01-31T11:56:00Z
2 2013-01-31T14:04:00Z
2 2013-03-11T16:08:00Z
And here's a SQL Fiddle for the above.
You stated that the order of the matching matters but it seems like you don't have anything to ORDER BY in table 1 to create a guaranteed order to match the other table and there is no way in SQL Server to order the rows after insertion date, because information about that is not stored. With this in mind it’s not possible to do a matching with the result you want. There is a solution to update the rows with an arbitrary match within each id. If that would be good enough.
UPDATE t
SET t.[date] = tt.[date]
FROM (SELECT *,
Row_number()
OVER (
partition BY id
ORDER BY [date]) AS rno
FROM Table1) AS t
INNER JOIN (SELECT *,
Row_number()
OVER (
partition BY id
ORDER BY [date]) AS rno
FROM Table2) AS tt
ON t.id = tt.id
AND t.rno = tt.rno
This solution will match all rows individually but can't guarantee the order.
DB Fiddle
Hi @vy ,
Welcome to the Microsoft SQL Server Q&A Forum!
Regarding your question, I checked some documents.The conclusion drawn from my own perspective is as follows:
When describing the contents of a table, most people usually display the rows in a specific order. But the table actually represents a collection, and the collection has no order. (Tables with clustered index added are stored in the order of the clustered index columns).
The virtual table(there is no order like a normal table) returned by the inner join operator is as follows:
id color id color
1 NULL 1 red
1 NULL 1 blue
The update statement returns a row from the virtual table to update the t1.color column. The column that satisfies the condition t1.id = c.id has two columns. It is uncertain which column is returned.SQL Server will return the row that happened to be accessed first.Therefore, different results may be produced, but they can all be considered correct. If you want to ensure the certainty of the results, you can choose to include a unique order by list.
Take the select statement as an example:
select top(1) *
from c
order by color
The above select statement specifies a unique order by list (the color field is unique), so the returned result is certain.
The result returned by the following statement is not certain (of course they are all considered correct):
select top(1) *
from c
order by id
select top(1) *
from c
In short, SQL Server will return the row that happens to be accessed first, and which row is accessed first is up to the developer.
If you have any question, please feel free to let me know.
If the response is helpful, please click "Accept Answer" and upvote it.
Regards
Echo
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It's not deterministic. Tom said "random", but that's inexact. As long as the query plan is the same, it is very likely that you will get the same value every time. At least if the plan is serial. But if the plan changes - you could also get a different value.
The important thing is that you cannot rely on anything here. Not even the value being randomly chosen.