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MySQL Removing Some Foreign keys
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You can use this to find foreign key constraints: SELECT * FROM information_schema.table_constraints WHERE constraint_schema = '<your db name>' AND constraint_type = 'FOREIGN KEY'
– Gayan Dasanayake
Aug 26 '17 at 2:48
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In JPA 2, using a CriteriaQuery, how to count results
...iaBuilder();
CriteriaQuery<Long> cq = qb.createQuery(Long.class);
cq.select(qb.count(cq.from(MyEntity.class)));
cq.where(/*your stuff*/);
return entityManager.createQuery(cq).getSingleResult();
Obviously you will want to build up your expression with whatever restrictions and groupings etc y...
Add list to set?
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With respect to sets, the | operator implements the set union operation. Both the |= operator and set.update() method apply that operation in-place and are effectively synonymous. So, set_a |= set_b could be considered syntactic sugar for both set_a.update(set_b) and set_a = set_a...
What is the difference between BIT and TINYINT in MySQL?
...deployed everything on linux, I had problems with queries that inserted or selected from tables that had BIT DATA TYPE.
Bit is not safe for now.
I changed to tinyint(1) and worked perfectly. I mean that you only need a value to diferentiate if it's 1 or 0 and tinyint(1) it's ok for that
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Does MySQL ignore null values on unique constraints?
... '1' for key 'x'
INSERT table1 VALUES (NULL);
INSERT table1 VALUES (NULL);
SELECT * FROM table1;
Result:
x
NULL
NULL
1
This is not true for all databases. SQL Server 2005 and older, for example, only allows a single NULL value in a column that has a unique constraint.
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Should I commit or rollback a read transaction?
... I create a temp table, populate it with ids, join it with a data table to select the data that goes with the ids, then delete the temp table. I'm really just reading data, and I don't care what happens to the temp table, since it's temporary... but from a performance perspective, would it be more ...
How to select all records from one table that do not exist in another table?
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SELECT t1.name
FROM table1 t1
LEFT JOIN table2 t2 ON t2.name = t1.name
WHERE t2.name IS NULL
Q: What is happening here?
A: Conceptually, we select all rows from table1 and for each row we attempt to find a row in table2 wi...
Which rows are returned when using LIMIT with OFFSET in MySQL?
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OFFSET is nothing but a keyword to indicate starting cursor in table
SELECT column FROM table LIMIT 18 OFFSET 8 -- fetch 18 records, begin with record 9 (OFFSET 8)
you would get the same result form
SELECT column FROM table LIMIT 8, 18
visual representation (R is one record in the table i...
How to create a SQL Server function to “join” multiple rows from a subquery into a single delimited
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If you're using SQL Server 2005, you could use the FOR XML PATH command.
SELECT [VehicleID]
, [Name]
, (STUFF((SELECT CAST(', ' + [City] AS VARCHAR(MAX))
FROM [Location]
WHERE (VehicleID = Vehicle.VehicleID)
FOR XML PATH ('')), 1, 2, '')) AS Locations
FROM [...
Why does “_” (underscore) match “-” (hyphen)?
...u want to use the underscore in like as a literal, you have to escape it:
select * from a where name like '%taz\_manual%.pdf%';
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