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ERROR 1452: Cannot add or update a child row: a foreign key constraint fails
... table. Following query would be helpful to fetch those non-matching rows:
SELECT child_table.*
FROM child_table
LEFT JOIN parent_table
ON parent_table.referenced_column = child_table.referencing_column
WHERE parent_table.referenced_column IS NULL
Now, you can generally do one (or more) of th...
How to find the most recent file in a directory using .NET, and without looping?
...ry.GetFiles()
orderby f.LastWriteTime descending
select f).First();
// or...
var myFile = directory.GetFiles()
.OrderByDescending(f => f.LastWriteTime)
.First();
share...
How do you version your database schema? [closed]
...bles. I then copy the data over from the old database using INSERT INTO x SELECT FROM y and then apply all indexes, constraints and triggers.
New tables, new columns, deleted columns all get handled automatically and with a few little tricks to adjust the copy routine I can handle column renames, ...
Postgres and Indexes on Foreign Keys and Primary Keys
...hema(s) from your program, all the information is on hand in the catalog:
select
n.nspname as "Schema"
,t.relname as "Table"
,c.relname as "Index"
from
pg_catalog.pg_class c
join pg_catalog.pg_namespace n on n.oid = c.relnamespace
join pg_catalog.pg_index ...
What is the difference between a schema and a table and a database?
...chema (tables he/she owns) however user can also see any schemas they have select priviliedges on. So a database can consist of hundreds of schemas, and each schema hundreds of tables. You can have tables with the same name in different schemas, which are in the same database.
A Table is a table, ...
T-SQL: Selecting rows to delete via joins
...
DELETE FROM TableA a WHERE [filter condition on TableA]
AND (a.BId IN (SELECT a.BId FROM TableB b JOIN TableA a
ON a.BId = b.BId
WHERE [filter condition on TableB]))
(Note Interbase doesn't support the AS keyword for aliases)
...
How do you track record relations in NoSQL?
...(A .NET based NoSQL Database with SQL support) your queries will be like
SELECT * FROM Comments WHERE userid = ‘That user’;
SELECT * FROM Comments WHERE pageid = ‘That user’;
SELECT * FROM Comments WHERE post-time > DateTime('2016, 1, 1');
SELECT * FROM Page WHERE tag = 'kendo'
...
Where is C not a subset of C++? [closed]
...
In C++, if you declare a struct, union, or enum, its name is immediately accessible without any qualifiers:
struct foo { ... };
foo x; // declare variable
In C, this won't work, because types thus declared live in their own distinct namespaces. Thus, you ...
How to see query history in SQL Server Management Studio
...been evicted, etc.), you may be able to find the query in the plan cache.
SELECT t.[text]
FROM sys.dm_exec_cached_plans AS p
CROSS APPLY sys.dm_exec_sql_text(p.plan_handle) AS t
WHERE t.[text] LIKE N'%something unique about your query%';
If you lost the file because Management Studio crashed, you...
Storing JSON in database vs. having a new column for each key
..._food pizza
.................
and query via something like this:
select meta_val from `table` where meta_key = 'name' and uid = 1 order by meta_id desc
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