Beginning SQL

Ideally, this first argument is the result you want returned. If it turns out to be NULL, however, then you
want the next argument to be the value that COALESCE() returns:
CONCAT(‘We have no details for ‘,CONCAT(CONCAT(FirstName,’ ‘),LastName))
This argument won’t return NULL so long as FirstName and LastName don’t contain NULL values.
However, if they do, then the final argument you pass is returned, and because the argument is a literal
string, it’s guaranteed to not be NULL:
‘No data available’
You can pass a considerable number of arguments to COALESCE(), though obviously each system has an
upper limit to the number of arguments that can be passed. That limit is fairly high, however.
Using INSERT INTO with
the SELECT Statement
This final section details how a SELECT statement can supply the data to be inserted into a table using
the INSERT INTO statement. Using these two statements in conjunction with one another is useful for
copying data from one table to another. For example, if you decide to restructure a database’s table
design but need to retain all the data, you would use the combination of INSERT INTO and SELECT
statements. You could create your new tables and then use INSERT INTO with SELECT to copy the data
over. The combination is also useful if you want to create a new identical copy of a database — for example,
for backup purposes or if you need to move the database to a new computer.
The basic syntax is as follows:
INSERT INTO destination_table_name
SELECT column_list FROM
source_table_name
WHERE condition
If you use this syntax, the destination columns and source columns must match. The number of columns
and appropriate data types must match, although there’s no need for column names to match. The
WHERE clause is optional and is needed only if you don’t want to copy over all records. For example, if
you want to create a copy of the Location table, first you need to create the table:
CREATE TABLE AnotherLocation
( LocationId int,
Street varchar(50),
City varchar(50),
State varchar(50)
);
After creating the table, you can copy over the data:
INSERT INTO AnotherLocation
SELECT LocationId, Street, City, State
FROM Location
WHERE State IN (‘New State’ ,’Golden State’);
Manipulating Data
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