Oracle SQL Plus The Definitive Guide- P24B docx

< previous page page_206 next page > < previous page page_207 next page > Page 207 PROJ_HOURS_FKTO_EMPLOYEE ENABLED FOREIGN KEY TO JEFF.EMPLOYEE EMPLOYEE_ID EMPLOYEE_ID PROJ_HOURS_FKTO_PROJECT ENABLED FOREIGN KEY TO JEFF.PROJECT PROJECT_ID PROJECT_ID HOURS_LOGGED_MUST_BE_INT CHECK ENABLED hours_logged = trunc(hours_logged) Indexes Two views return information about indexes. Each index gets an entry in the ALL_INDEXES view, and the ALL_IND_COLUMNS view returns the columns included in each index. Listing Indexes for a Table The problem of listing indexes for a table is much the same as that of listing constraints on a table. You have a master- detail relationship between the index and its columns, and you may have multiple indexes on one table. There are two approaches you can take. One approach is to write a script that describes one particular index, while the other is to write a script that lists all indexes on a table. The tradeoff between these two approaches is that one lets you look at indexes by name, while the other lets you look at indexes by table. The problem is that you probably need both ways. Sometimes, as when a unique index is violated, you do need to look up an index by name. Other times, you just want to see what indexes have been defined on a particular table. One thing to keep in mind when working with unique indexes is that Oracle will report a unique index violation as if it were a constraint violation. The error message you get is the same as the one used when you violate a unique constraint, and it looks like this: ORA-00001: unique constraint (JEFF.UNIQUE_BILLING_RATE) violated The reason for this is no doubt because Oracle enforces both unique and primary key constraints by creating indexes on the constrained fields. If you do get the error message just shown, there are two things you might want to check. First, list the constraints on the table you are updating. If you don't find one with a name that matches the one in the error message, check to see if there happens to be a unique index with that same name. The SHOW_INDEX script in the next section will help you do this. < previous page page_207 next page > < previous page page_208 next page > Page 208 Beginning with Oracle8i, it is possible to define a unique or primary key constraint without having a corresponding index created. Index Scripts. Since the previous section, Table Constraints, showed you how to write one script to list all constraints, let's take the opposite approach this time and write a script that describes just one index. Following that, I'll show how you can expand on that first script by writing a second script that does list indexes by table. You can have it both ways. The SHOW_INDEX.SQL script Shown below is a SQL*Plus script that describes just one index. The first part of the script resembles the other scripts shown in this chapter. It looks at the input argument to see whether or not it was qualified by an owner name, defaults it to the current user's userid if necessary, then stores the results in the substitution variables s_owner_name and s_index_name. Next, a SELECT is done on the ALL_INDEXES table to retrieve information that is not column- specific about the index into a set of substitution variables. These substitution variables are then used to define the page title. So far, nothing has been displayed to the user. Finally, the index columns themselves are selected, causing the page title to print. If the index does not exist, no columns will be selected and the page title will not be printed. The result will be that there is no output for the user to see. To avoid leaving the user in doubt about why there is no output, an extra SELECT is done to cover this case. This final SELECT statement only succeeds if the index does not exist, and it outputs a message informing the user that is the case. The last thing the script does is reset anything it changed back to the default values. Here is the script: DESCRIPTION Displays information about an index. The index name is passed as a parameter to this script. INPUTS param 1 Name of the index to be described. SET ECHO OFF SET RECSEP OFF SET NEWPAGE NONE < previous page page_208 next page > < previous page page_209 next page > Page 209 SET VERIFY OFF SET PAGESIZE 9999 SET HEADING OFF SET LINESIZE 80 SET FEEDBACK OFF CLEAR COMPUTES CLEAR COLUMNS CLEAR BREAKS Turn off terminal output to avoid spurious blank lines caused by the SELECTS that are done only to load the substitution variables. SET TERMOUT OFF Dissect the input argument, and get the owner name and table name into two separate substitution variables. The owner name defaults to the current user. DEFINE s_owner_name = DEFINE s_index_name = COLUMN owner_name NOPRINT NEW_VALUE s_owner_name COLUMN index_name NOPRINT NEW_VALUE s_index_name SELECT DECODE(INSTR( &&1, .), O,USER, /*Default to current user.*/ UPPER(SUBSTR(&&1,1,INSTR(&&1,.)-1))) owner_name, DECODE(INSTR (&&1,.), 0,UPPER (&&1), /*Only the index name was passed in.*/ UPPER(SUBSTR(&&1,INSTR(¦& 1 & rsquo;,.)+1))) index_name FROM dual; Retrieve information about the index as a whole. DEFINE s_table_owner DEFINE s_table_name DEFINE s_index_type DEFINE s_uniqueness DEFINE s_tablespace_name COLUMN table_owner NOPRINT NEW_VALUE s_table_owner COLUMN table_name NOPRINT NEW_VALUE s_table_name COLUMN index_type NOPRINT NEW_VALUE s_index_type COLUMN uniqueness NOPRINT NEW_VALUE s_uniqueness COLUMN tablespace_name NOPRINT NEW_VALUE s_tablespace_name SELECT table_owner, table_name, index_type, uniqueness, tablespace_name FROM all_indexes WHERE owner = &&s_owner_name AND index_name = &&s_index_name; Information about the index as a whole is printed in the page title. TTITLE SKIP 1 LEFT INDEX &&s_owner_name &&s_index_name - &&s_index_type &&s_uniqueness SKIP 1 - DEFINED ON TABLE &&s_table_owner &s_table_name SKIP 1 - STORED IN TABLESPACE & &_tablespace_name SKIP 1- CONTAINING COLUMNS: < previous page page_209 next page > < previous page page_210 next page > Page 210 List the columns that make up the index. The indent column moves the column list over to the right so that it comes after the CONTAINING COLUMNS: portion of the header. SET TERMOUT ON COLUMN indent FORMAT A19 COLUMN column_name FORMAT A30 SELECT indent, column_name FROM all_ind_columns WHERE index_owner = &&s_owner_name AND index_name = &&s_index_name ORDER BY column_position; Spit out an error message if the index does not exist. TTITLE SKIP 1 SELECT Index &&s_owner_name &&s_table_name does not exist. FROM DUAL WHERE NOT EXISTS ( SELECT * FROM all_indexes WHERE owner =&&s_owner_name AND index_name = &&s_index_name ); Change all settings back to defaults CLEAR COLUMNS CLEAR BREAKS UNDEFINE s_owner_name UNDEFINE s_index_name UNDEFINE s_index_type UNDEFINE s_uniqueness UNDEFINE s_tablespace_name SET PAGESIZE 14 SET HEADING ON SET NEWPAGE 1 SET FEEDBACK ON Running the SHOW_INDEX script To describe an index, simply invoke SHOW_INDEX and pass the index name as a parameter. Here's an example: SQL> @show_index project_hours_pk INDEX JEFF.PROJECT_HOURS_PK NORMAL UNIQUE DEFINED ON TABLE JEFF.PROJECT_HOURS STORED IN TABLESPACE USERS CONTAINING COLUMNS: PROJECT_ID EMPLOYEE_ID TIME_LOG_DATE < previous page page_210 next page > < previous page page_211 next page > Page 211 If the specified index does not exist, you will get a message telling you that. For example: SQL> @show_index this_does_not_exist Index JEFF.THIS_DOES_NOT_EXIST does not exist. Next you will see how you can write another script that uses SHOW_INDEX to describe all the indexes on a table. The LIST_INDEXES.SQL script You now have a script that describes one specific index. If you wanted to describe all the indexes for a particular table, the obvious solution would be to run SHOW_INDEX for each of those indexes. The only thing that makes this at all difficult is that SQL*Plus has no built-in looping construct. You can't just write a simple loop to display each index for a table. However, you do have a view, the ALL_INDEXES view, from which you can select the names of all the indexes on a table. Instead of selecting just the index names, it's not too big a leap to select an expression such as this: SELECT @SHOW_INDEX ¦¦ owner ¦¦ . ¦¦ index_name Executing a SELECT such as the previous one against the ALL_INDEXES view results in output that looks like this: @SHOW_INDEX JEFF.PROJECT_HOURS_PK @SHOW_INDEX JEFF.PROJECT_HOURS_UNIQUE Using the SPOOL command, you can send this output to a file, which will then contain commands to describe each index on a table. Then you execute that file. The following LIST_INDEXES.SQL script does this: DESCRIPTION Describe all the indexes that are defined on the specified table. INPUTS param 1 The table name, optionally qualified by an owner name using the standard dot notation. SET ECHO OFF SET TERMOUT OFF SET FEEDBACK OFF SET VERIFY OFF CLEAR COLUMNS Dissect the input argument, and get the owner name and table name into two separate substitution variables. The owner name defaults to the current user. DEFINE s_owner_name = < previous page page_211 next page > < previous page page_212 next page > Page 212 DEFINE s_table_name = COLUMN owner_name NOPRINT NEW_VALUE s_owner_name COLUMN table_name NOPRINT NEW_VALUE s_table_name SELECT DECODE (INSTR (&&, .), 0,USER, /*Default to current user.*/ UPPER(SUBSTR(&&1,1,INSTR(&&1,.)-1))) owner_name, DECODE (INSTR (&&1 ,.), 0,UPPER(&&1), /*Only the table name was passed in.*/ UPPER(SUBSTR(&&1,INSTR(&&1,.)+1))) table_name FROM dual; Create a file of commands that will use the SHOW_INDEX script to describe each index defined on the table. SET PAGESIZE 0 SET HEADING OFF SPOOL list_indexes_1. sql Generate the show index commands. SELECT @SHOW_INDEX ¦¦ owner ¦¦ . ¦¦ index_name FROM all_indexes WHERE table_owner = &&s_owner_name AND table_name = &&s_table_name; Generate an error message if the table does not exist. SELECT PROMPT Table &&s_owner_name &&s_table_name does not exist. FROM DUAL WHERE NOT EXISTS ( SELECT * FROM all_tables WHERE owner = &&s_owner_name AND table_name = &&s_table_name ); Generate a message if no indexes at all exist for the table. SELECT PROMPT Table &&s_owner_name &&s_table_name has no indexes defined. FROM all_tables WHERE owner = &&s_owner_name AND table_name = &&s__table_name AND NOT EXISTS ( SELECT * FROM all_indexes WHERE table_owner = &&s_owner_name AND table_name = &&s_table_name ); SPOOL OFF Reset everything back to its default. SET PAGESIZE 14 SET TERMOUT ON SET FEEDBACK ON SET VERIFY ON < previous page page_212 next page > < previous page page_213 next page > Page 213 CLEAR COLUMNS Tell the user what she is going to see. PROMPT PROMPT INDEXES DEFINED ON TABLE &&s_owner_name &s_table_name Execute the script that was just created to display all the indexes on the table. @list_indexes_1 This script builds a file named LIST_INDEXES_1, which runs the SHOW_INDEX script for each index on the specified table. There are two extra SELECTs to cover the cases where the table does not exist, or where there are no indexes defined on the table. This file is then executed in order to display information about each of the table's indexes. Running the LIST_INDEXES.SQL script Here's what it looks like to run the LIST_INDEXES script on the PROJECT_HOURS table: SQL> @list_indexes project_hours INDEXES DEFINED ON TABLE JEFF. PROJECT_HOURS INDEX JEFF.PROJECT_HOURS_UNIQUE NORMAL UNIQUE DEFINED ON TABLE JEFF.PROJECT_HOURS STORED IN TABLESPACE USERS CONTAINING COLUMNS: PROJECT_ID EMPLOYEE_ID TIME_LOG_DATE HOURS_LOGGED DOLLARS_CHARGED INDEX JEFF.PROJECT_HOURS_PK NORMAL UNIQUE DEFINED ON TABLE JEFF.PROJECT_HOURS STORED IN TABLESPACE USERS CONTAINING COLUMNS: PROJECT_ID EMPLOYEE_ID TIME_LOG_DATE As you can see, information about each index on the PROJECT_HOURS table is displayed. The next two examples show the results of running LIST_INDEXES with an invalid table name and for a table that does not have any indexes: SQL> @list_indexes bad_table_name INDEXES DEFINED ON TABLE JEFF.BAD_TABLE_NAME Table JEFF.BAD_TABLE_NAME does not exist. SQL> SQL> @list_indexes x < previous page page_213 next page > < previous page page_214 next page > Page 214 INDEXES DEFINED ON TABLE JEFF.X Table JEFF.X has no indexes defined. Triggers Information about triggers can be retrieved from two views, the ALL_TRIGGERS view and the ALL_TRIGGER_COLS view. Most of the time you will be able to find all the information you need in ALL_TRIGGERS. The ALL_TRIGGER_COLS view contains a list of all database columns referenced in the trigger. This view is sometimes useful when you are troubleshooting because it can quickly show you which triggers reference or modify any given database column. Looking at Trigger Definitions Retrieving the definition of a trigger from the database actually turns out to be quite easy compared to the effort you go through to see indexes and constraints. Mostly this is because you don't have a master/detail relationship to deal witheverything you need is in the ALL_TRIGGERS view. The DESCRIPTION field Oracle includes in the view helps a lot too. Everything you need to see is in just four columns. There are just a couple of caveats you need to be aware of when looking at the ALL_TRIGGERS view. The first is that the format of the data in the DESCRIPTION and TRIGGER_BODY fields comes from the original CREATE TRIGGER statement. This can lead to some minor inconsistencies from one trigger to the next, depending on where the line breaks occur and whether the CREATE TRIGGER statement was entered in upper- or lowercase. There's also no guarantee that lines of code in the trigger body won't exceed your line length. For that reason, I usually set line length fairly high when I look at a trigger. The second caveat is that the WHEN clause is returned as one long line in the WHEN_CLAUSE field, regardless of whether or not it was on one line in the original CREATE TRIGGER statement. Neither of these issues presents any great problem. It just helps to be aware of them. Trigger Scripts The following sections describe scripts that will let you list trigger definitions. The SHOW_TRIGGER.SQL script The following script shows the definition and code for a trigger on a table. Note the use of FOLD_BEFORE in the COLUMN commands. This results in the four col- < previous page page_214 next page > . ways. The SHOW_INDEX .SQL script Shown below is a SQL* Plus script that describes just one index. The first part of the script resembles the other scripts shown in this chapter. It looks at the. if the index does not exist, and it outputs a message informing the user that is the case. The last thing the script does is reset anything it changed back to the default values. Here is the. > Page 210 List the columns that make up the index. The indent column moves the column list over to the right so that it comes after the CONTAINING COLUMNS: portion of the header. SET