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Articles on Trending Technologies
Technical articles with clear explanations and examples
How to use a function for default value in MySQL?
We cannot use a function for default value in MySQL, but we can use triggers. Let us see an example. First, we will create a table. The CREATE command is used to create a table. mysql> CREATE table TbLFunctionTrigger - > ( - > id int, - > username varchar(100) - > ); Query OK, 0 rows affected (0.55 sec) The following is the syntax to create a trigger and include a default value. CREATE TRIGGER anyName BEFORE INSERT ON yourTableName FOR EACH ROW ...
Read MoreWhich one is preferred between a large table or multiple small tables in MySQL?
It is very difficult to say whether to prefer one large table or multiple small tables. It depends − On the application we are using. On database normalization However, there are many key points, through which we can say that multiple small tables are good in that situation. Suppose many developers are going to develop multiple tables, then there is a need to split them into multiple small tables. A situation when you are giving authority to many developers. This authority is for different parts of data. In this case, a need arise to split into multiple small ...
Read MoreDifference between two timestamps in seconds in MySQL?
Let us now see the following methods to calculate the time difference between two timestamps in seconds. Method The following is the query to calculate the difference between two timestamps. mysql> SELECT TIMESTAMPDIFF(SECOND, '2018-10-17 11:51:55', '2018-10-17 11:51:58'); The following is the output in seconds. +---------------------------------------------------------------------+ | TIMESTAMPDIFF(SECOND, '2018-10-17 11:51:55', '2018-10-17 11:51:58') | +---------------------------------------------------------------------+ | ...
Read MoreInstruction type MVI r, d8 in 8085 Microprocessor
MVI is a mnemonic, which actually means “Move Immediate”. With this instruction, we can load a register with an 8-bitsor 1-Bytevalue. This instruction supports immediate addressing mode for specifying the data in the instruction. In the instruction “d8” stands for any 8-bit data, and ‘r’ stands for any one of the registers e.g. A, B, C, D, E, H or L. So this r can replace any one of the seven registers. As ‘r’ can have any of the seven register names, so there are seven opcodes for this type of instruction. It occupies 2-Bytes in the memory. ...
Read MoreMyISAM versus InnoDB in MySQL?
Both are engine types. Here is the query by which we can get to know which engine type and tables are being used. Firstly, we will choose the database with the help of USE command − mysql> USE business; Database changed Here is the query through which we can know which table or engine is being used − mysql> SHOW table status; The following is the output +------------------------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+-------------+------------+--------------------+----------+----------------+---------+ |Name | Engine | Version | Row_format | ...
Read MoreRank function in MySQL?
The rank() function can be used to give a rank for every row within the partition of a result set. First, let us create a table − mysql> create table RankDemo mysql> ( mysql> id int mysql> ); Query OK, 0 rows affected (0.53 sec) Inserting records into table. mysql> insert into RankDemo values(1); Query OK, 1 row affected (0.19 sec) mysql> insert into RankDemo values(3); Query OK, 1 row affected (0.12 sec) mysql> insert into RankDemo values(3); Query OK, 1 row affected (0.11 ...
Read MoreHow to do a batch insert in MySQL?
To do a batch insert, we need to use all column names with parenthesis, separated by ‘, ’. Let us see an example. First, we will create a table. The following is the CREATE command to create a table. mysql> CREATE table MultipleRecordWithValues - > ( - > id int, - > name varchar(100) - > ); Query OK, 0 rows affected (0.88 sec) The following is the syntax of batch insert. INSERT into yourTableName values(column1, column2, ....N), (column1, column2, ....N), (column1, column2, ....N), ...........N; ...
Read MoreInstruction type MOV r1, r2 in 8085 Microprocessor
In 8085 Instruction set, MOV is a mnemonic, which stands for “MOVe”. In this instruction 8-bit data value in register r2 will be moved to the 8-bit register r1. Note that in 8085 instructions, as the first operand specifies the destination, and the second one the source, so here also r1 is destination register and r2 is the source register. This instruction uses register addressing for specifying the data. Here, “r1” and “r2”can be any one of the following registers. r1, r2 = A, B, C, D, E, H, or L As r1 can have any one of ...
Read MoreWhen should I use a composite index in MySQL?
The composite index can be used when we are using sub queries. The advantages of using composite index are in case of. Joining Filtering Selecting The following is the syntax of index. index(column_name1, column_name2, column_name3, column_name4, ............................N) Let us create a table first and within that we have set index. mysql> create table MultipleIndexDemo - > ( - > id int, - > FirstName varchar(100), - > LastName varchar(100), - > Address varchar(200), - > index(id, LastName, ...
Read MoreWhat is the operator <=> in MySQL?
Here are the usages of the operator in MySQL. Case 1 This operator is similar to = operator i.e. when the value is equal then the result will become true(1), otherwise false(0). In the first case both = and operators work same. Case 2 Whenever we compare any value with NULL then the operator gives the value 0 and when we compare with NULL NULL, then it returns 1. While in case of = operator, this does not happen. Whenever we compare any value with NULL, it returns NULL. If we compare NULL with NULL, then ...
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