SQL Server Foundation

1.select query columns, restrictions on columns, where filter rows, restrictions on rows; Group by set operations, such as averaging; having a limit on the value of a set operation, such as a mean greater than 30;order by to the collation limit (default increment)

2.f5 execution, effect equivalent to execute

3.select top from table; detect the first 100 rows of data

4. Order by;　Select Id,name,price from Product order by name Desc,price; Sort by name in descending order, and then increment by price in the same name

Select Id,name,price from Product order by 2; Ascending sort by the second column (that is, the name column)

5. IsNull function: Determine whether a certain data is empty;

Select ID, Name, isnull (Price, ") from Product order by name Desc,price; In order not to bother the user, if Price is null, the result of the query will be empty

6. As Keyword: alias table columns:

Select ID, Name, isnull (Price, ") as price123 from Product order by name Desc,price; After IsNull (price, ") operation, the original price column is not listed, this time give the column name price123

7. + Keyword: Connect "columns" to "strings":

Select ID, name, price, name + ' product prices are ' + CONVERT (varchar,price) from product order by name Desc,price; CONVERT (varchar,price) data type conversion, the price of money type to varchar type to facilitate string concatenation

8. Arithmetic expression: +-*/

Select ID, name, rate as ' hourly wage ', round (rate*40*52,1) as ' annual salary ', round (rate*40*52,0) as ' annual salary ' from Employee; Round (rate*40*52,1) after the decimal point is rounded to retain 1 bits, round (rate*40*52,0) rounding not decimal places

Select ID, name, rate as ' hourly wage ', (rate+5) *40*52 as ' annual salary ' from Employee; (rate+5) *40*52 Change the priority of operations

　　

　　　　

　　　　　　

SQL Server Foundation