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MySQL Articles
Page 132 of 355
Why we cannot use MySQL DATE data type along with time value?
The default format for MySQL DATE data type is “YYYY-MM-DD” and in this format, there is no possibility to store the time value. Hence, we can say that we cannot use DATE data type along with time value.As we can see in the following example MySQL returns only date value even on using time along with the date.mysql> select DATE("2017-09-25 09:34:21"); +-----------------------------------+ | DATE("2017-09-25 09:34:21") | +-----------------------------------+ | 2017-09-25 | +-----------------------------------+ 1 row in set (0.04 sec)However, in DATETIME and TIMESTAMP date data types we can use the time to date.
Read MoreHow to search a record by date in MySQL table?
Suppose we have a table ‘Order123’ having ProductName, Quantity and OrderDate columns as follows −mysql> Select * from Order123; +-------------+----------+------------+ | ProductName | Quantity | OrderDate | +-------------+----------+------------+ | A | 100 | 2017-05-25 | | B | 105 | 2017-05-25 | | C | 55 | 2017-05-25 | | D | 250 | 2017-05-26 | | E | 500 | 2017-05-26 | | ...
Read MoreWhat happens if I will delete a row from MySQL parent table?
While deleting the row from the parent table, if the data of that row is used in the child table then MySQL will throw an error because of the failure of FOREIGN KEY constraint. It can be understood with the example of two tables named ‘customer’ and ‘orders’. Here, ‘customer’ is the parent table and ‘orders’ is the child table. We cannot delete a row, that is used in child table ‘orders’, from the ‘customer’ table. It can be demonstrated by deleting the values from the parent table as follows −mysql> Select * from Customer; +----+--------+ | id | name ...
Read MoreWhen are two tables connected with MySQL FOREIGN KEY then how can we say that the integrity of data is maintained in child table?
Actually, foreign keys enforce referential integrity that helps us to maintain the consistency and integrity of the data automatically. It can be understood with the example of two tables named ‘customer’ and ‘orders’. Here, ‘customer’ is the parent table and ‘orders’ is the child table. We cannot create an order for a non-existent customer. It can be demonstrated by inserting the values in both the tables as follows −mysql> Select * from Customer; +----+--------+ | id | name | +----+--------+ | 1 | Gaurav | | 2 | Raman | | 3 | Harshit| | 4 | Aarav | ...
Read MoreIn case of FOREIGN KEY constraint, what kind of relationship is there between MySQL parent and child tables?
The relationship between parent and child table is One-to-Many relationship. It can be understood with the example of two tables named ‘customer’ and ‘orders’. Here, ‘customer’ is the parent table and ‘orders’ is the child table. The relationship is one-to—many because a customer can have more than one order. It can be demonstrated by inserting the values in both the tables as follows −mysql> Select * from Customer; +----+---------+ | id | name | +----+---------+ | 1 | Gaurav | | 2 | Raman | | 3 | Harshit | | 4 | Aarav | +----+---------+ ...
Read MoreHow can we drop UNIQUE constraint from a MySQL table?
For dropping UNIQUE constraint from a MySQL table, first of all, we must have to check the name of the index created by the UNIQUE constraint on the table. As we know that SHOW INDEX statement is used for this purpose. The ‘key_name’ in the result set of SHOW INDEX statement contains the name of the index. Now either with the help of DROP INDEX statement or ALTER TABLE statement, we can drop the UNIQUE constraint. The syntax for both the statements is as follows −SyntaxDROP INDEX index_name ON table_name; OR ALTER TABLE table_name DROP INDEX index_name;ExampleSuppose we have the ...
Read MoreHow can we create multicolumn UNIQUE indexes?
For creating multicolumn UNIQUE indexes we need to specify an index name on more than one column. Following example will create a multicolumn index named ‘id_fname_lname’ on the columns ‘empid’, ’first_name’, ’last_name’ of ‘employee’ table −mysql> Create UNIQUE INDEX id_fname_lname on employee(empid, first_name, last_name); Query OK, 0 rows affected (0.41 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> describe employee; +------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +------------+-------------+------+-----+---------+-------+ | empid | int(11) | YES | MUL | NULL | | | first_name | varchar(20) | YES | | NULL | | | ...
Read MoreIn SAP database, Importing table columns with /'s in the name
I would suggest you to use BCP utility to perform an import/export of data to a text file in SQL Server. When you run below command, it loads data to a text file.BCP Db.TN out "Location of the text file " -c -S ServerName –TNow if you want to load data to SQL Server from a flat file, you can use this:BCP Db.TN in "Location of the text file " -c -S ServerName –TYou can also try editing Mappings while loading data from a flat file.
Read MoreImporting data from Pgsql to SAP HANA database
Import and Export using a flat file is the easiest option. You can use CSV file if it is a onetime activity. However, If you think it is a repetitive activity then I would suggest you use HANA ETL options like HANA SLT replication, Smart Data access, etc.SAP HANA Replication allows migration of data from source systems to SAP HANA database. Simple way to move data from existing SAP system to HANA is by using various data replication techniques.System replication can be set up on the console via command line or by using HANA studio. The primary ECC or transaction ...
Read MoreRunning a SQL query from specific month in SAP DB
When your T0.name is char filed, you should replace Order By as below −order by case when cast(left (T0.Name,2) as int)>=8 then cast(left (T0.Name,2) as int)-8 else cast(left (T0.Name,2) as int)+4 end
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