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how to emulate “insert ignore” and “on duplicate key update” (sql merge) with postgresql?
...meant that you use a query like this: "start transaction; create temporary table temporary_table as select * from test where false; copy temporary_table from 'data_file.csv'; lock table test; update test set data=temporary_table.data from temporary_table where test.id=temporary_table.id; insert into...
How do you determine what SQL Tables have an identity column programmatically
...umns in SQL Server 2005 that have identity columns and their corresponding table in T-SQL.
13 Answers
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MySQL, Check if a column exists in a table with SQL
I am trying to write a query that will check if a specific table in MySQL has a specific column, and if not — create it. Otherwise do nothing. This is really an easy procedure in any enterprise-class database, yet MySQL seems to be an exception.
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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 with the same value fo...
Scraping html tables into R data frames using the XML package
How do I scrape html tables using the XML package?
4 Answers
4
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How can foreign key constraints be temporarily disabled using T-SQL?
... database just run this code:
-- disable all constraints
EXEC sp_MSforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"
To switch them back on, run: (the print is optional of course and it is just listing the tables)
-- enable all constraints
exec sp_MSforeachtable @command1="print '?'", @command...
How to get size of mysql database?
...
Run this query and you'll probably get what you're looking for:
SELECT table_schema "DB Name",
ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) "DB Size in MB"
FROM information_schema.tables
GROUP BY table_schema;
This query comes from the mysql forums, where there are more c...
Change auto increment starting number?
In MySQL, I have a table, and I want to set the auto_increment value to 5 instead of 1 . Is this possible and what query statement does this?
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avoid page break inside row of table
I want to avoid page break inside row of table in html, when I convert html to PDF by wkhtmltopdf. I use page-break-inside:avoid with table- its works, but I have so many rows,
then not work.
If set display of tr as block or some thing else then it change the formatting of table and insert double...
What is the difference between JOIN and UNION?
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Joins and Unions can be used to combine data from one or more tables. The difference lies in how the data is combined.
In simple terms, joins combine data into new columns. If two tables are joined together, then the data from the first table is shown in one set of column alongside t...