Reading this original article on The Code Project will help you a lot: Visual Representation of SQL Joins. Also check this post: SQL SERVER – Better Performance – LEFT JOIN or NOT IN?. Find original one at: Difference between JOIN and OUTER JOIN in MySQL.
SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @your_date)) for example SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, GETDATE())) gives me 2008-09-22 00:00:00.000 Pros: No varchar<->datetime conversions required No need to think about locale
If you are on SQL Server 2017 or Azure, see Mathieu Renda answer. I had a similar issue when I was trying to join two tables with one-to-many relationships. In SQL 2005 I found that XML PATH method can handle the concatenation of the rows very easily. If there is a table called STUDENTS SubjectID … Read more
SELECT name, email, COUNT(*) FROM users GROUP BY name, email HAVING COUNT(*) > 1 Simply group on both of the columns. Note: the older ANSI standard is to have all non-aggregated columns in the GROUP BY but this has changed with the idea of “functional dependency”: In relational database theory, a functional dependency is a … Read more
Try: mysql -u username -p database_name < file.sql Check MySQL Options. Note 1: It is better to use the full path of the SQL file file.sql. Note 2: Use -R and –triggers to keep the routines and triggers of original database. They are not copied by default. Note 3 You may have to create the … Read more
The correct way to avoid SQL injection attacks, no matter which database you use, is to separate the data from SQL, so that data stays data and will never be interpreted as commands by the SQL parser. It is possible to create an SQL statement with correctly formatted data parts, but if you don’t fully … Read more
Why is it needed? When data is stored on disk-based storage devices, it is stored as blocks of data. These blocks are accessed in their entirety, making them the atomic disk access operation. Disk blocks are structured in much the same way as linked lists; both contain a section for data, a pointer to the … Read more
Syntax: ALTER TABLE {TABLENAME} ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE} WITH VALUES Example: ALTER TABLE SomeTable ADD SomeCol Bit NULL –Or NOT NULL. CONSTRAINT D_SomeTable_SomeCol –When Omitted a Default-Constraint Name is autogenerated. DEFAULT (0)–Optional Default-Constraint. WITH VALUES –Add if Column is Nullable and you want the Default Value for Existing Records. Notes: … Read more