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author | tpearson <tpearson@283d02a7-25f6-0310-bc7c-ecb5cbfe19da> | 2010-01-20 01:29:50 +0000 |
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committer | tpearson <tpearson@283d02a7-25f6-0310-bc7c-ecb5cbfe19da> | 2010-01-20 01:29:50 +0000 |
commit | 8362bf63dea22bbf6736609b0f49c152f975eb63 (patch) | |
tree | 0eea3928e39e50fae91d4e68b21b1e6cbae25604 /kexi/doc/dev/kexi_alter_table.txt | |
download | koffice-8362bf63dea22bbf6736609b0f49c152f975eb63.tar.gz koffice-8362bf63dea22bbf6736609b0f49c152f975eb63.zip |
Added old abandoned KDE3 version of koffice
git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/applications/koffice@1077364 283d02a7-25f6-0310-bc7c-ecb5cbfe19da
Diffstat (limited to 'kexi/doc/dev/kexi_alter_table.txt')
-rw-r--r-- | kexi/doc/dev/kexi_alter_table.txt | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/kexi/doc/dev/kexi_alter_table.txt b/kexi/doc/dev/kexi_alter_table.txt new file mode 100644 index 00000000..4a6c851e --- /dev/null +++ b/kexi/doc/dev/kexi_alter_table.txt @@ -0,0 +1,110 @@ +----------------------- +KEXI ALTER TABLE ISSUES +----------------------- + +1. PROBLEMS +- different databases have different set of altering capabilities + (SQLite has no table altering capabilities at all; re-creation is needed: + this has high cost in time and disk space for large tables) +- we need to collect every detailed change made in Table Designer and apply + these changes to existing table schema +- in the case when a table is already filled with data, we need to perform + tasks to move that data to a new structure, + especially if database engine can't do it for us or if the engine + wants simply drop the data because convertion cannot be done automatically +- because of above issues, some work needs to be done at the client side + +2. What can be altered using ALTER TABLE: +2.1 Inserting columns + (into a specified position) + ADD COLUMN <column_definition> [FIRST | AFTER <col_name> ] + + (adding many colums at the end) + ADD COLUMN <column_definition>,... + +2.2 Adding constraints, indices + ADD INDEX [<index_name>] [<index_type>] (<index_col_name>,...) + + ADD CONSTRAINT [<symbol>] PRIMARY KEY [<index_type>] (<index_col_name>,...) + + ADD CONSTRAINT [<symbol>] UNIQUE [<index_name>] [<index_type>] (<index_col_name>,...) + + ADD CONSTRAINT [<symbol>] FOREIGN KEY [<index_name>] (<index_col_name>,...) + [<reference_definition>] + +2.3 Altering column properties + ALTER COLUMN <col_name> {SET DEFAULT <literal> | DROP DEFAULT} + + CHANGE COLUMN <old_col_name> column_definition [FIRST|AFTER <col_name>] + + (rename column) + CHANGE <old_column> <new_column> + + MODIFY COLUMN <column_definition> [FIRST | AFTER <col_name>] + +2.4 Dropping + DROP COLUMN <col_name> + + DROP PRIMARY KEY + + DROP INDEX <index_name> + + DROP FOREIGN KEY <fk_symbol> + +2.5 Renaming a table + RENAME TO <new_tbl_name> + + +3. How to perform table altering be re-creation: +SQLite: (taken from Ticket 236: Add RENAME TABLE + - will be easier to work around missing ALTER TABLE + http://www.sqlite.org/cvstrac/tktview?tn=236,8) + Currently the recommended method to ALTER TABLE is: + + 1. Create a temporary table. + 2. Copy all data from original table to temporary table. + 3. Drop the original table. + 4. Create a new table. + 5. Copy all data from the temporary table to the new table. + +For example, suppose you have a table named "t1" with columns +names "a", "b", and "c" and that you want to delete column "c" +from this table. The following steps illustrate how this could be done: + +BEGIN TRANSACTION; +CREATE TEMPORARY TABLE t1_backup(a,b); +INSERT INTO t1_backup SELECT a,b FROM t1; +DROP TABLE t1; +CREATE TABLE t1(a,b); +INSERT INTO t1 SELECT a,b FROM t1_backup; +DROP TABLE t1_backup; +COMMIT; + +If the table name also changes on altering, it's easier to do the +altering (no temp. table needed): + +BEGIN TRANSACTION; +CREATE TABLE t2(c,d); +INSERT INTO t2 (c,d) SELECT a,b FROM t1; +DROP TABLE t1; +COMMIT; + + If we had RENAME TABLE, we'd get easier alter table here: + 1. Rename original table to temp name. + 2. Create new table with ORIGINAL name. + 3. Move data from previous to new table. + 4. Drop previous table. + +4. PROPOSED ALGORITHM + + + +5. Useful documentation + http://dev.mysql.com/doc/mysql/en/ALTER_TABLE.html + + +6. Document History +2004-07-20 js + Started + Asked Richard Hipp about RENAME TABLE + |