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If L1 and L2 are list objects containing keys and respective values, following list comprehension syntax can be used to construct dictionary object. >>> L1 = ['a','b','c','d'] >>> L2 = [1,2,3,4] >>> d = {L1[k]:L2[k] for k in range(len(L1))} >>> d {'a': 1, 'b': 2, 'c': 3, 'd': 4}
Actually, in simple words, we can say that a join between tables is an extension of a single-table SELECT statement but it involves the additional complexities:Need to specify all the tablesWe need to specify all the tables in FROM clause which are involved in the join. It is in contrast with the SELECT statement in which only one table name is necessary.Need to specify the matching conditionsWe just need to specify the matching conditions based on which a join matches the records in one table with a record in another table. The conditions often are given in the WHERE clause, ... Read More
JAVA_HOME refers to jdk/bin directory. It is used by a java based application.
Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator.Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.CategoryOperatorAssociativityPostfix>() [] . (dot operator)Left to rightUnary>++ - - ! ~Right to leftMultiplicative>* /Left to rightAdditive>+ -Left to rightShift>>> >>> >= < == !=Left to rightBitwise AND>&Left to rightBitwise XOR>^Left to rightBitwise OR>|Left to ... Read More
MySQL NOT RLIKE operator can be used to check for a pattern which is not present within an expression. The syntax for NOT RLIKE is as follows − Syntax NOT RLIKE Pat_not_for_match Here Pat_not_for_match is the pattern which is not to be matched with the expression. Example mysql> Select Id, Name from Student WHERE Name NOT RLIKE '^H'; +------+---------+ | Id | Name | +------+---------+ | 1 | Gaurav | | 2 | Aarav | | 20 | Gaurav | ... Read More
JavaScript handling of the variable is different from other programming languages C, C++., Java, etc. Variables in JavaScript can be thought of as named containers. You can place data into these containers and then refer to the data simply by naming the container. Before you use a variable in a JavaScript program, you must declare it. Variables are declared with the var keyword as follows. var rank; var points; Storing a value in a variable is called variable initialization. You can do variable initialization at the time of variable creation or at a ... Read More
In SAP HANA, Persistence layer is used for handling all operational and transaction data to take secure backup and restoring data incase of corruption or database crash. It provides use of Save point which can be used for restoring data.With use of concept of persistence layer of SAP’s relational database, it ensures the successful data restores. Besides managing log data on the disk, HANA’s persistence layer allows read and write data operations via all storage interfaces.Persistence layer in HANA ensures that database can be restored to the most recent committed state after a restart or after a system crash and ... Read More
In Python 2.x, both != and operators are available to check if two operands are not equal. Both return true if operands are not equal and false if they are equal.In Python 3.x, operator has been deprecated.
By using DISTINCT keyword along with column name as the argument of COUNT() function we can count the number of unique values in a column. The syntax is as follows − SELECT COUNT(DISTINCT Col_name) FROM table_name; Example Suppose we have the following table mysql> Select * from tender; +----------+--------------+--------------+-------+ | clientid | client_Fname | Client_Lname | value | +----------+--------------+--------------+-------+ | 100 | Mohan | Kumar | 60000 | | 101 | Sohan ... Read More
The toString(Object[] a) method of the java.util.Arrays class returns a string representation of the contents of the specified Object array. If the array contains other arrays of elements, they are converted to strings by the Object.toString() method inherited from Object, which describes their identities rather than their contents. Example import java.util.Arrays; public class ArrayDemo { public static void main(String[] args) { Object[] ob1 = new Object[] { 10, 20 }; System.out.println("The array is:"); for (Object number ... Read More