SQL 3 for interview preparation-Data Management

1. T-SQL condition expression:

(1). Constant: contains one or more letters, numbers, or symbols (! @ #) Composition

(2). unary operator: Only one operand operator + represents an integer-represents a negative number ~ Complement Operator

(3) binary operator: the operator that combines two operands contains the arithmetic operator value assignment operator (=) bit operator comparison operator logical operator String concatenation operator (+) or unary operator

==><=<> (Not equal )! (Not)

 

(4). '_': a character like 'C _ 'must contain at least two characters

%: Any length string a like 'C %'

[]: A like '[1-9]' for data within the specified range

[^]: Data not in the specified range

(5). logical operators: And or not

The in keyword is used to limit multiple returned values.

 

2. T-SQL insert data

Insert into Table Name (column, column, column ...) Values (Value column ,,,)

 

Add existing table dataNew existing tableMedium: inster into newtable new table (column) Select column from old table (this can be noted: like English: insert query data from old table to new table)

Add existing table dataThe new table does not exist.Medium: Select column into new table from old table

The preceding statement cannot be specified. Therefore, we need to create a new ID column. The syntax is as follows:

Select other columns, identity (data type, identification seed, identification growth) as column name

Into new table

Form old table

 

Merge data using the Union keyword for insertion

 

Insert table name (column name)

Select column value Union

Select column value Union

Select column value Union

Select column Value

Union is not required for the last row.

 

3. Update data with T-SQL

Update table name set column name = new value where Condition

 

4. Use T-SQL to delete data

Delete from table name where Condition