大约有 37,000 项符合查询结果（耗时：0.0311秒） [XML]
ERROR: Error 1005: Can't create table (errno: 121)
... constraints use the following SQL query:
SELECT
constraint_name,
table_name
FROM
information_schema.table_constraints
WHERE
constraint_type = 'FOREIGN KEY'
AND table_schema = DATABASE()
ORDER BY
constraint_name;
Look for more information there, or try to see where the error o...
Split comma-separated strings in a column into separate rows
...approach but modified according to Rich Scriven's comment,
Jaap's two data.table methods and two dplyr / tidyr approaches,
Ananda's splitstackshapesolution,
and two additional variants of Jaap's data.table methods.
Overall 8 different methods were benchmarked on 6 different sizes of data frames u...
Giving a border to an HTML table row,
Is it possible to border a table row, <tr> in one go instead of giving a border to individual cells, <td> like,
...
Add a column to a table, if it does not already exist
I want to write a query for MS SQL Server that adds a column into a table. But I don't want any error display, when I run/execute the following query.
...
Make a DIV fill an entire table cell
...nswered) and we have CSS3! Is there any way to get a div to fill an entire table cell's width and height using CSS?
26 Answ...
What is InnoDB and MyISAM in MySQL?
...er on their locking implementation: InnoDB locks the particular row in the table, and MyISAM locks the entire MySQL table.
You can specify the type by giving MYISAM OR InnoDB while creating a table in DB.
share
|
...
Any way to select without causing locking in MySQL?
...h-nolock.aspx
in MS SQL Server you would do the following:
SELECT * FROM TABLE_NAME WITH (nolock)
and the MYSQL equivalent is
SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED ;
SELECT * FROM TABLE_NAME ;
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ ;
EDIT
Michael Mior sugg...
Improving bulk insert performance in Entity framework [duplicate]
I want to insert 20000 records in a table by entity framework and it takes about 2 min. Is there any way other than using SP to improve its performance. This is my code:
...
Add column to SQL Server
I need to add a column to my SQL Server table. Is it possible to do so without losing the data, I already have?
5 Answers...
How do you delete a column by name in data.table?
...
Any of the following will remove column foo from the data.table df3:
# Method 1 (and preferred as it takes 0.00s even on a 20GB data.table)
df3[,foo:=NULL]
df3[, c("foo","bar"):=NULL] # remove two columns
myVar = "foo"
df3[, (myVar):=NULL] # lookup myVar contents
# Method 2a ...