大约有 5,887 项符合查询结果（耗时：0.0102秒） [XML]
Postgres: How to do Composite keys?
... error, and omit the redundant CONSTRAINT (already implied), too:
CREATE TABLE tags
(
question_id INTEGER NOT NULL,
tag_id SERIAL NOT NULL,
tag1 VARCHAR(20),
tag2 VARCHAR(20),
tag3 VARCHAR(20),
PRIMARY ...
Delete all Duplicate Rows except for One in MySQL? [duplicate]
How would I delete all duplicate data from a MySQL Table?
2 Answers
2
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Cloning a MySQL database on the same MySql instance
... you... There's no way to do this within MySQL afaik (except by hand, one table / view at a time)
– Greg
Mar 23 '09 at 21:50
42
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What are the possible values of the Hibernate hbm2ddl.auto configuration and what do they do
...this option is used it does not drop the whole schema instead it drops the tables whose mappings are available while running this. For example if a database with Schema S has A, B, C tables and java code has mappings for A and B only then Hibernate will not drop the table C.
– ...
Assign multiple columns using := in data.table, by group
What is the best way to assign to multiple columns using data.table ? For example:
2 Answers
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Create unique constraint with null columns
I have a table with this layout:
4 Answers
4
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User recognition without cookies or local storage
... $totalRun = 0;
$yin = 0;
// Trains RNA until it gets stable
while ($keepTrainning == true) {
// Sweeps each row of the input subject
foreach ($input as $row_counter => $row_data) {
// Finds out the number of columns the input ha...
How do I get the last inserted ID of a MySQL table in PHP?
I have a table into which new data is frequently inserted. I need to get the very last ID of the table. How can I do this?
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Generate GUID in MySQL for existing Data?
I've just imported a bunch of data to a MySQL table and I have a column "GUID" that I want to basically fill down all existing rows with new and unique random GUID's.
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php is null or empty?
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As is shown in the following table, empty($foo) is equivalent to $foo==null and is_null($foo) has the same function of $foo===null. The table also shows some tricky values regarding the null comparison. (ϕ denotes an uninitialized variables. )
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