• Create table Emp( ); → DDL command
• ; is known as delimiter (terminator), it indicates end of command
• SQL commands are case insensitive
• Tablename and column name are case-insensitive for MySQL under Windows

Insert

insert into emp values('1', 'Amit', 5000, 'Mumbai', '1995-01-15');

• When you are inserting the data is case sensitive.
• For char, varchar, date, time, and datetime use Single Quotes
  • Recommended
    • insert into emp(empno, city, ename, sal, dob) values(’2’, ‘Delhi’, ‘King’, 6000, ‘1990-02-20’);
    • Because
      • Readable
      • Flexible
      • In Future, if you ALTER the table and add a column, this INSERT statement will continue to work and all program using this INSERT statement are not affected.

Null value

• Null means nothing, 0(48) and space(32) counts as values because they have ASCII values.

• Null value is having ASCII value 0

• Special treatment is given to null value in all RDBMS

• Null value is independent of datatype (you can INSERT null value for a column of any datatype)

• Null value occupies only 1 Byte of storage

• If you specify null value fir the last column, or if the row is ending with null value then all those columns will not occupy any space

• Those columns that are likely to have large number of null values, preferably they should be specified at the end of the table structure to conserve on HD space

  • Note: This needs to be planned at the beginning ask the client which columns have null values. Then you can put all those columns having large number of null values at the end of table. This will save large amount of storage in HardDisk.

  

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