T-SQL judgment exists (database, table, stored procedure, constraints ...) and columns)

determine if the database exists

If db_id (N ' DATABASENAME ') is not null

the methods for judging tables, views, stored procedures, and cursors are summarized as follows:

use databasename--jump to the specified database    

go  

if object_id (n ' a ', n ' U ') is not null  

drop Table a  

go  

Note: A is a table and U represents a data table type

Type code similar to U, as shown below

Object type:

AF = aggregate function (CLR)

C = CHECK Constraint

D = DEFAULT (constrained or standalone)

F = FOREIGN KEY constraint

PK = PRIMARY KEY constraint

P = SQL Stored Procedure

PC = assembly (CLR) stored procedure

FN = SQL scalar function

FS = assembly (CLR) scalar functions

FT = assembly (CLR) table-valued function

R = Rule (Legacy, standalone)

RF = Replication filtering process

SN = synonym

TR = SQL DML Trigger

IF = SQL Inline Table-valued function

TF = SQL Table-valued function

U = table (user-defined type)

UQ = UNIQUE Constraint

V = view

X = Extended Stored Procedure

IT = Internal table

I've introduced sysobjects this system table before. Custom tables, stored procedures ..... will be stored in this form. So.....

Whether the columns in the table exist

  if col_length (  ,    ' C '   is     not     null      

Note: A is a table name

    c is the column name 

Or:

Select   *    fromsyscolumnswhereid=object_id (' table name ')    and   name=' column name ' 

Note: A description record of this column is returned, and there is no return null;

T-SQL judgment exists (database, table, stored procedure, constraints ...) and columns)