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Postgis installation: type “geometry” does not exist
...eate table with Postgis. I do it by this page . But when I import postgis.sql file, I get a lot of errors:
10 Answers
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Postgres: INSERT if does not exist already
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@TusharJain prior to PostgreSQL 9.5 you can do an "old fashioned" UPSERT (with CTE) but you may experience problems with race conditions and it will not be performant as 9.5 style. There is a good detail about upsert on this blog (in the updated area at...
MySQL ON vs USING?
In a MySQL JOIN , what is the difference between ON and USING() ? As far as I can tell, USING() is just more convenient syntax, whereas ON allows a little more flexibility when the column names are not identical. However, that difference is so minor, you'd think they'd just do away with USI...
Which are more performant, CTE or temporary tables?
...y to other constructs that can also be used as inline table expressions in SQL Server. Derived tables, Views, and inline table valued functions. Note that whilst BOL says that a CTE "can be thought of as temporary result set" this is a purely logical description. More often than not it is not materl...
SQL Server indexes - ascending or descending, what difference does it make?
When you create an index on a column or number of columns in MS SQL Server (I'm using version 2005), you can specify that the index on each column be either ascending or descending. I'm having a hard time understanding why this choice is even here. Using binary sort techniques, wouldn't a lookup be ...
MySQL: selecting rows where a column is null
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SQL NULL's special, and you have to do WHERE field IS NULL, as NULL cannot be equal to anything,
including itself (ie: NULL = NULL is always false).
See Rule 3 https://en.wikipedia.org/wiki/Codd%27s_12_rules
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Copy a table from one database to another in Postgres
...it directly to the target database:
pg_dump -t table_to_copy source_db | psql target_db
Note: If the other database already has the table set up, you should use the -a flag to import data only, else you may see weird errors like "Out of memory":
pg_dump -a -t my_table my_db | psql target_db
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How to escape apostrophe (') in MySql?
The MySQL documentation says that it should be \' . However, both scite and mysql shows that '' works. I saw that and it works. What should I do?
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Read data from SqlDataReader
I have a SQL Server 2008 database and I am working on it in the backend. I am working on asp.net/C#
13 Answers
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What is the difference between Scope_Identity(), Identity(), @@Identity, and Ident_Current()?
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This is a role model answer. In particular, working with SQL and SQL Server can be weird, and this explains things in a very clear, layman's manner, while still being fairly informative. It doesn't sound like something being communicated between two database specialists, which a L...