I have a table like this:
// mytable
+----+-------------------------------------------+
| id | col |
+----+-------------------------------------------+
| 1 | Peter|423421 , Alex Jon|61333 |
| 2 | Barmar|624321 |
| 3 | Jack|624321 , Ali|312331 , Leonard|624321 |
+----+-------------------------------------------+
I need to check second row if isn't containing 824326, then add this value , Sara|824326 in the end of that. Something like this:
| 2 | Barmar|624321 , Sara|824326 |
Now I want to know, how can I check that field isn't containing thins number 824326 ?
Here is my try, I just need to the condition (to check existing)
UPDATE mytable
SET col = CASE WHEN col = {:val doesn't exist} // <= How to write this condition?
THEN CONCAT(col,':newval')
ELSE SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = "It is duplicate";
END,
WHERE id = 2;
Note1: :newval is this , Sara|824326 in the above query.
Note2: :val is this 824326 in the above query.
You have to use INSTR. Try this:
UPDATE mytable
SET col = CASE WHEN col INSTR(col, ':val') = 0
THEN CONCAT(col,':newval')
ELSE SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = "It is duplicate";
END,
WHERE id = 2;
Related
Consider the following table.
myTable
+----+-----------+------------------------------------+
| Id | responseA | responseB |
+----+-----------+------------------------------------+
| 1 | | {"foo":"bar","lvl2":{"key":"val"}} |
+----+-----------+------------------------------------+
where:
Id, INT (11) PRIMARY
responseA, TEXT utf8_unicode_ci
responseB, TEXT utf8_unicode_ci
Let's say that I want to conditionally update the table with some outside data. The conditions are:
• if there's nothing in responseA, populate it with the outside data, otherwise
• if there is something in responseA, leave it as it is, and populate responseB with the outside data
I was pretty much convinced that I could just do this to get what I want:
UPDATE myTable
SET
responseA = IF(TRIM(responseA) = '','foo',TRIM(responseA)),
responseB = IF(TRIM(responseA) != '','foo',TRIM(responseB))
WHERE Id = 1
However, this updates both responseA and responseB to the same value - foo, making the table:
myTable
+----+-----------+-----------+
| Id | responseA | responseB |
+----+-----------+-----------+
| 1 | foo | foo |
+----+-----------+-----------+
I was expecting my table to look like this after the update:
myTable
+----+-----------+------------------------------------+
| Id | responseA | responseB |
+----+-----------+------------------------------------+
| 1 | foo | {"foo":"bar","lvl2":{"key":"val"}} |
+----+-----------+------------------------------------+
What am I misunderstanding, and how can I achieve this conditional update? Do the updates happen sequentially? If so, I guess that would explain why both of the fields are updated.
UPDATE TABLE
SET responseA = CASE WHEN responseA IS NULL
THEN #data
ELSE responseA
END,
responseB = CASE WHEN responseA IS NULL
THEN responseB
ELSE #data
END
;
here your changed query
UPDATE myTable
SET
responseB = IF(TRIM(responseA) != '','foo',TRIM(responseB)),
responseA = IF(TRIM(responseA) = '','foo',TRIM(responseA))
WHERE Id = 1
It seems the value of responseA is changed before the IF() for responseB is evaluated.
One possible solution is to do a simple UPDATE:
UPDATE mytable SET responseA = ? WHERE id = 1
Then adjust the columns in a trigger, where you have access to both the original and the new value of the columns:
CREATE TRIGGER t BEFORE UPDATE ON mytable
FOR EACH ROW BEGIN
IF TRIM(OLD.responseA) != '' THEN
SET NEW.responseB = NEW.responseA;
SET NEW.responseA = OLD.responseA;
END IF;
END
(I have not tested this.)
I am also assuming that your test for '' (empty string) instead of NULL is deliberate, and that you know that NULL is not the same as ''.
The key point in the UPDATE statement is that you should update first the column responseB, so that column responseA retains its original value which can be checked again when you try to update it:
UPDATE myTable
SET responseB = CASE WHEN TRIM(responseA) = '' THEN responseB ELSE 'foo' END,
responseA = CASE WHEN TRIM(responseA) = '' THEN 'foo' ELSE responseA END
WHERE Id = 1;
i have table like this
-----------------------
id | name | is_default|
------------------------
1 | a | 1 |
2 | a | 0 |
3 | a | 0 |
4 | a | 0 |
-----------------------
now i want to change line 2(id =2) is_default to 1,and origin line(id =1) id_default to 0 at the same time,like the choose default option in list in UI.
1.can i do this in one sql statement?
2.if it is possible,how to write the sql statement or how to write in mybatis mapper.xml?
Springboot with mybatis ,sql statement write in mapper.xml
#Data
pulbic class Option{
private Integer id;
private String name;
private Boolean isDefault;
}
how to write the mybatis or mysql statement?
You may use a CASE expression:
UPDATE yourTable
SET is_default = CASE WHEN id = 1 THEN 0 ELSE 1 END
WHERE id IN (1, 2);
Or, if you intended to just toggle the default values for id 1 and 2, then try:
UPDATE yourTable
SET is_default = CASE WHEN is_default = 1 THEN 0 ELSE 1 END
WHERE id IN (1, 2);
Tim's answer is fine. If the values are only 0/1, you can simplify it to:
UPDATE t
SET is_default = 1 - is_default
WHERE id IN (1, 2);
I have a column in users table named permissions. Like this:
// users
+---------+-----------------+-------------+
| id | permissions | name |
+---------+-----------------+-------------+
| int(11) | bit(15) | varchar(20) |
+---------+-----------------+-------------+
| 1 | 001100001111101 | Jack |
| 2 | 111111111111111 | Peter |
| 3 | 110000000111011 | Martin |
+---------+-----------------+-------------+
As you can see, permissions column has bit(15) datatype. Each bit of that value determines one user ability. For example, the first bit refers to voting-ability, the second one refers to commenting-ability ant etc ...
Also I have a trigger BEFORE UPDATE which investigates that permission like this:
SELECT permissions INTO #deleting_permission FROM users WHERE id = new.deleter_id;
IF old.deleted <> new.deleted THEN
IF (IFNULL((#deleting_permission & b'10000000000' > 0), 0) < 1) THEN
SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = "You cannot delete post";
END IF;
END IF;
And always it throws:
You cannot delete post
Even for #2 user which has 111111111111111 permission value. So what's wrong?
Noted that I update permissions column like this:
-- To give some specific accesses (permissions) to the user
UPDATE users SET permissions = b'111111000101011' WHERE id = ?
-- To give full access (permissions) to the user
UPDATE users SET permissions = -1 WHERE id = ?
You select the field active in the trigger to check permission, but according to your question, the rights are held in the permissions field.
Change your query to use the latter field:
SELECT `permissions` INTO #active_deleter FROM users WHERE id = new.deleter_id;
Also, your permissions field has 15 bits. The mask you use has only 10. You should check if you are testing the right bit in the first place.
If you want to work with the BIT type, then you'll need to use bitwise operators, not regular operators. For example, if you wanted to check if the user had the left most bit set as a permission, you could do an & operation:
SELECT permissions INTO #p FROM users WHERE id = new.deleter_id;
IF old.deleted <> new.deleted THEN
IF (b'100000000000000' & #p = 0)
THEN
SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = "You cannot delete post";
END IF;
END IF;
The basic idea above is that the literal b'100000000000000' serves as a mask which can be used to detect if the left most bit (and only that bit) is set to 1. If it were set to 1, then the & operation would not return 0.
The reason why a user with 111111111111111 permissions has all rights is that any mask checking a bit would return true.
I have a table like this:
| id | address | name | oid | state | event_id | ctrl |
-------------------------------------------------------------------
| 1 | test_addr_1 | test_1 | 25.345.17 | 1 | 0 | 15 |
I need to get event_id while update data in row.
I want to do something like this:
If new name not equals with old name event_id = event_id + 1
If new oid not equals with old oid event_id = event_id + 2
If new state not equals with old state event_id = event_id + 4
If new ctrl bigger then old ctrl event_id = event_id + 8
# Params to procedure
PROCEDURE Write(IN pAddr VARCHAR(20), IN pName VARCHAR(20), IN pOid VARCHAR(20), IN pState TINYINT, IN pCtrl INT)
#procedure body
SET #ev = 0;
SELECT
CASE
WHEN name != pName THEN SET #ev = #ev + 1
WHEN oid != pOid THEN SET #ev = #ev + 2
WHEN state != pState THEN SET #ev = #ev + 4
WHEN ctrl > pCtrl THEN SET #ev = #ev + 8
END
FROM table1
UPDATE table1 SET ..... , event_id = #ev WHERE address = pAddr
How can I do it? Or will it be better to make it not with the help of SQL?
As already suggested, an audit trigger can be used here to ensure that changes from all sources are caught. However, I suggest two changes:
1) audit tables - use other tables to hold audit data, as these tables tend to grow and it is not recommended to mix operational and auditing data in the same structures (even in the same database)
2) use more friendly change flag - from your example, it seems that you are setting bits in an integer value. While this provides compact data (catch many changes within a single integer), it requires more convoluted operations to see when the name has changed for example. The audit table can simply have BIT(1) columns like nameChanged, oidChanged etc.
CREATE TRIGGER table1Audit BEFORE UPDATE ON <table1>
FOR EACH ROW BEGIN
SET #ev =
(CASE WHEN OLD.name != NEW.name THEN 1 ELSE 0 END) +
(CASE WHEN OLD.oid != NEW.oid THEN 2 ELSE 0 END) +
(CASE WHEN OLD.state != NEW.state THEN 4 ELSE 0 END) +
(CASE WHEN OLD.ctrl != NEW.ctrl THEN 8 ELSE 0 END)
-- INSERT INTO someaudittable
--'table1', #ev
END;
Solved! Thanks to #Alexei.
I wanted to know, why the row was added to the history table.
The result is:
CREATE TRIGGER SetReason BEFORE UPDATE ON <table1>
FOR EACH ROW BEGIN
SET NEW.event_id =
(CASE WHEN OLD.name != NEW.name THEN 1 ELSE 0 END) +
(CASE WHEN OLD.oid != NEW.oid THEN 2 ELSE 0 END) +
(CASE WHEN OLD.state != NEW.state THEN 4 ELSE 0 END) +
(CASE WHEN OLD.ctrl != NEW.ctrl THEN 8 ELSE 0 END)
END;
I have a table which has a structure as:
ID DBInstance DBName Tag
1 | INS1 | master | NULL
2 | INS1 | tempdb | NULL
4 | INS2 | master | NULL
5 | INS2 | tempdb | NULL
I want to update the tag in this table as based on the condition as:
1) Update tag as "a" only for DBInstance as "INS1" and DBName as "master"
2) Update tag as "b" only for DBInstance as "INS2" and DBName as "tempdb".
And I want to update both of these two only in a single statement, not in two different update queries. How can I do so?
A query somewhat like this:
UPDATE tbl_test
SET tag = 'a' where DBInstance in ('INS1') and DBName IN ('master'),
tag = 'b' where DBInstance in ('INS2') and DBName IN ('tempdb')
But obviously, this query is wrong, so how can I do so?
You can use the case when then like this:
UPDATE tbl_test
SET tag = case
when DBInstance = 'INS1' and DBName = 'master'
then 'a'
when DBInstance = 'INS2' and DBName = 'tempdb'
then 'b'
else NULL -- or may be tag, or default value which you want.
end